Class 8

Students can Download Maths Chapter 2 Measurements Ex 2.3 Questions and Answers, Notes Pdf, Samacheer Kalvi 8th Maths Book Solutions Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 2 Measurements Ex 2.3

Question 1.
Fill in the blanks:
(i) The three dimensions of a cuboid are _____.
(ii) The meeting point of more than two edges- is called as ______.
(iii) A cube has _____ faces.
(iv) The cross section of a solid cylinder is ______.
(v) If a net of a 3-D shape has six plane squares, then it is called ______.
Solution:
(i) length, breadth and height
(ii) vertex
(iii) six
(iv) circle
(v) cube

Question 2.
Match the following:

Solution:
(i) b
(ii) a
(iii) d
(iv) c

Question 3.
Which 3-D shapes do the following nets represent? Draw them.

Solution:
(i) The net represents cube, because it has 6 squares

(ii) The net represents cuboid

(iii) The net represents Triangular prism

(iv) The net represents square pyramid

(v) The net represents cylinder

Question 4.
For each solid, three views are given. Identify for each solid, the corresponding top, front and side (T, F & S) views.

Solution:

Question 5.
Verify Euler’s formula for the table given below

Solution:
Euler’s formula is given by F + V – E
(i) F = 4 ; V = 4; E = 6
F + V – E = 4 + 4 – 6 = 8 – 6
F + V – E = 2
∴ Euler’s formula is satisfied.

(ii) F = 10; V = 6; E = 12
F + V – E = 10 + 6 – 12
= 16 – 12 = 4 ≠ 2
∴ Euler’s formula is not satisfied.

(iii) F = 12 ; V = 20 ; E = 30
F + V – E = 12 + 20 – 30
= 32 – 30 = 2
∴ Euler’s formula is satisfied.

(iv) F = 20 ; V = 13 ; E = 30
F + V – E = 20 + 13 – 30
= 33 – 30 = 3 ≠ 2
∴ Euler’s formula is not satisfied.

(v) F = 32 ; V = 60 ; E = 90
F + V – E = 32 + 60 – 90
= 92 – 90 = 2
∴ Euler’s formula is satisfied.

Question 6.
Find the area of the given nets.

Solution:
(i) Area = Area of 6 squares of side 4 cm
= 6 × a² sq. units
= 6 × 4 × 4 cm²
= 96 cm²
(ii) Area = Area of 2 rectangles of
l = 10, b = 6 + Area of 2 rectangles of l = 6, b = 4 + Area of 2 rectangles of l= 10,b = 4
= (10 × 6) + (6 × 4)+ (10 × 4) cm²
= 60 + 24 + 40 cm²
= 124 cm²

Question 7.
Can a polyhedron have 12 faces, 22 edges and 17 vertices?
Solution:
By Euler’s formula F + V- E = 2 fora polyhedron.
Here F = 12, V = 17, E = 22
F + V – E = 12 + 17 – 22
= 29 – 22
= 7 ≠ 2
∴ The polyhedron cannot have 12 faces 22 edges and 17 vertices.

Students can Download Maths Chapter 1 Rational Numbers Ex 1.3 Questions and Answers, Notes Pdf, Samacheer Kalvi 8th Maths Book Solutions Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 1 Rational Numbers Ex 1.3

Question 1.
Match the following appropriately.

Solution:
(i) 5
(ii) 4
(iii) 2
(iv) 3
(v) 1

Question 2.
Which of the following properties hold for subtraction of rational numbers? Why?
(a) closure
(b) commutative
(c) associative
(d) identity
(e) inverse
Solution:
(i) For subtraction of rational numbers closure property is true.
Because for any two rational number a and b, a + b is in Q.
Eg. \(-\frac{1}{4}+\frac{3}{2}=\frac{-1+6}{4}=\frac{5}{4}\) is rational.
(ii) Commutative fails as \(\frac{1}{3}-\frac{2}{4} \neq \frac{2}{4}-\frac{1}{3}\)
(iii) Associative fails as \(\frac{1}{2}-\left(\frac{1}{3}-\frac{1}{4}\right) \neq\left(\frac{1}{2}-\frac{1}{3}\right)-\frac{1}{4}\)
(iv) Identity fails as 5 – 0 ≠ 0 – 5
(v) Inverse also fails.

Question 3.
Subbu spends \(\frac{1}{3}\) of his monthly earnings on rent, \(\frac{2}{5}\) on food and \(\frac{1}{10}\) on monthly usuals. What fractional part of his earnings is left with him for other expenses?
Solution:

Question 4.
In a constituency, \(\frac{19}{25}\) of the voters had voted for candidate A whereas \(\frac{7}{50}\) had voted for candidate B. Find the fraction of the voters who had voted for other.
Solution:

Question 5.
If \(\frac{3}{4}\) of a box of apples weighs 3 kg and 225 gm, how much does a full box of apples weigh?

Solution:
Let the total weight of a box of apple = x kg.
Weight of \(\frac{3}{4}\) of a box apples = 3 kg 225 gm. = 3.225 kg
\(\frac{3}{4}\) × x = 3225
x = \(\frac{3.225 \times 4}{3}\) kg
= 1.075 × 4 kg = 4.3 kg = 4 kg 300 gm
Weight of the box of apples = 4 kg 300 gm.

Question 6.
Mangalam buys a water jug of capacity 3\(\frac{4}{5}\) litres. If she buys another jug which is 2\(\frac{2}{3}\) times as large as the smaller jug, how many litres can the larger one hold?

Solution:

Question 7.
In a recipe making, every \(1 \frac{1}{2}\) cup of rice requires \(2 \frac{3}{4}\) cups of water. Express this in the ratio of rice to water.
Solution:
For the recipe rice required = \(1 \frac{1}{2}\) cup; water required = \(2 \frac{3}{4}\) cups

∴ rice : water = 6 : 11

Question 8.
Ravi multiplied \(\frac{25}{8}\) and \(\frac{16}{15}\) to obtain \(\frac{400}{120}\). He says that the simplest form of this product is \(\frac{10}{3}\) and Chandru says the answer in the simplest form is \(3 \frac{1}{3}\). Who is correct? or Are they both correct? Explain.
Solution:

Question 9.
A piece of wire is \(\frac{4}{5}\) m long. If it is cut into 8 pieces of equal length, how long will each piece be?
Solution:
Length of the wire = \(\frac{4}{5}\) m = \(\frac{4 \times 100}{5}\) cm = 80 cm
Number of equal pieces made from it = 8 Length of a single piece = 80 ÷ 8 = 10 cm
Length of each small pieces = 10 cm.

Question 10.
Find the length of a room whose area is \(\frac{153}{10}\) sq.m and whose breadth is \(2 \frac{11}{20}\) m.
Solution:
Breadth of the room = \( 2\frac{11}{20}\) m; Area of the room = \(\frac{153}{10}\) sq.m
Length of the room × Breadth = Area of the room

Length of the room = 6 m

Challenging Problems

Question 1.
Show that

Solution:

Question 2.
If A walks \(\frac{7}{4}\) km and then jogs \(\frac{3}{5}\) km, find the total distance covered by A. How much did A walk rather than jog?
Solution:
Distance walked by A = \(\frac{7}{4}\) km; Distance jogged by A = \(\frac{3}{5}\) km

Question 3.
In a map, if 1 inch refers to 120km, then find the distance between two cities B and C which are \(4 \frac{1}{6}\) inches and \(3 \frac{1}{3}\) inches from the city A which is in between the cities B and C.

Solution:
1 inch = 120 km

Distance between B and C = 900 km

Question 4.
Give an example for each of the following statements.
(i) The collection of all non-zero rational numbers is closed under division.
(ii) Subtraction is not commutative for rational numbers.
(iii) Division is not associative for rational numbers.
(iv) Distributive of multiplication over subtraction is true for rational numbers, that is a (b – c) = ab – ac.
(v) The mean of two rational numbers is rational and lies between them.
Solution:
(i) Let a = \(\frac{5}{4}\) and b = \(\frac{-4}{3}\) be two non zero rational numbers.
a ÷ b = \(\frac{5}{6} \div \frac{-4}{3}=\frac{5}{6} \times \frac{3}{-4}=\frac{5}{-8}\) is in Q
∴ Collection of non-zero rational numbers are closed under division.

∴ Division is not associative for rational numbers

∴ From (1) and (2)
a × (b – c) = ab – bc
∴ Distributivity of multiplication over subtraction is true for rational numbers.

Question 5.
If \(\frac{1}{4}\) of a ragi adai weighs 120 grams, 4what will be the weight of \(\frac{2}{3}\) of the same ragi adai?
Solution:
Let the weight of 1 ragi adai = x grams given \(\frac{1}{4}\) of x = 120 gm
\(\frac{1}{4}\) × x = 120
x = 120 × 4
x = 480 gm
∴ \(\frac{2}{3}\) of the adai
= \(\frac{2}{3}\) × 480 gm = 2 × 160 gm = 320 gm
\(\frac{2}{3}\) of the weight of adai = 320 gm

Question 6.
Find the difference between the greatest and the smallest of the following rational numbers.
\(\frac{-7}{12}, \frac{2}{-9}, \frac{-11}{36}, \frac{-5}{-6}\)
Solution:
Here \(\frac{-5}{-6}=\frac{5}{6}\) and is a positive rational number.
All other numbers are negative numbers
∴ \(\frac{-5}{-6}\) is the greatest number
LCMof 12, 9, 36 = 3 × 4 × 3 = 36

Question 7.
If p + 2q = 18 and pq = 4o, find \(\frac{2}{p}+\frac{1}{q}\)
Solution:
Given p + 2q = 18 …………… (1)
pq = 40 ………… (2)

Question 8.
Find ‘x’ \(5 \frac{x}{5} \times 3 \frac{3}{4}\) = 21.
Solution:

Question 9.
The difference between a number and its two third is 30 more than one -fifth of the number. Find the numbers.
Solution:
Let the number to be find out = x
Its two third = \(\frac{2 x}{3}\)
Given x – \(\frac{2}{3}\) x = \(\frac{1}{5}\) x + 30

Question 10.
By how much does \(\frac{1}{\frac{10}{11}}\) exceed \(\frac{1}{\frac{10}{11}}\)?
Solution:

Students can Download Maths Chapter 4 Geometry Intext Questions and Answers, Notes Pdf, Samacheer Kalvi 8th Maths Book Solutions Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 4 Geometry Intext Questions

Answer the following questions:

Question 1.
The sum of the three angles of a triangle is ______
Solution:
1800

Question 2.
The exterior angle of a triangle is equal to the sum of the _______ angles opposite to it.
Solution:
interior

Question 3.
In a triangle, the sum of any two sides is ____ than the third side.
Solution:
greater

Question 4.
The difference between any two sides of a triangle is _______ than the third side.
Solution:
Smaller

Question 5.
Angles opposite to equal sides are ______ and vice-versa.
Solution:
Equal

Question 6.
The angles of a triangle are in the ratio 4 : 5 : 6
(i) Is it an acute, right or obtuse triangle?
(ii) Is it scalene, isosceles or equilateral?
Solution:
(i) Given the angles of a triangle are in the ratio 4 : 5 : 6 Sum of three angles of a
triangle = 180°.
Let the three angles 4x, 5x and 6x
4x + 5x + 6x = 180°
15x = 180° [∵ Vertically opposite angles are equal]

∴ x = 12°
∴ The angles are 4x ⇒ 4 × 12 = 48°
5x ⇒ 5 × 12 = 60°
6x ⇒ 6 × 12 = 72°
∴ The angle of the triangle are 48°, 60°, 72°
∴ It is an acute angles triangle.

(ii) We know that the sides opposite to equal angles are equal.
Here all the three angles are different.
∴ The sides also different.
∴ The triangle is a scalene triangle.

Question 7.
What is ∠A in the triangle ABC?

Solution:
The exterior angle = sum of interior opposite angles.
∴ ∠A + ∠C = 150° in ∆ABC
But ∠C = 40° [∵ Vertically opposite angles are equal]

Question 8.
Can a triangle have two supplementary angles? Why?
Solution:
Sum of three angles of a triangle is 180°.
∴ Sum of any two angles in a triangle will be less than 180°.
∴ A triangle cannot have two supplimentary angles.

Question 9.
________ shapes have the same shapes but different sizes.
Solution:
Similar

Question 10.
shapes are exactly the same in shape and size.
Solution:
Congruent

Exercise 4.1

Try these Page No. 99

Identify the pairs of shapes which are similar and congruent.

Similar shapes:
(i) W and L
(ii) B and J
(iii) A and G
(iv) B and J
(v) B and Y
Congruent shapes:
(i) Z and I
(ii) J and Y
(iii) C and P You can find more.
(iv) B and K
(v) R and S
(vi) I and Z

Try these Page No. 108

Question 1.
Match the following by their congruence

Solution:
1 – (iv)
2 – (iii)
3 – (i)
4 – (ii)

Try this Page No. 108

Question 1.
In the figure, DA = DC and BA = BC. Are the triangles DBA and DBC congruent? Why?
Solution:

Here AD = CD
AB = CB
DB = DB (common)
∆DBA ≅ ∆DBC [∵ By SSS Congruency]
Also RHS rule also bind here to say their congruency.

Exercise 4.3

Try this Page No. 114

Question 1.
Is it possible to construct a quadrilateral PQRS with PQ = 5 cm, QR = 3 cm, RS = 6 cm, PS = 7 cm and PR = 10 cm. If not, why?
Solution:
The lower triangle cannot be constructed as the sum of two sides 5 + 3 = 8 < 10 cm. So this quadrilateral cannot be constructed.

Students can Download Maths Chapter 1 Rational Numbers Ex 1.2 Questions and Answers, Notes Pdf, Samacheer Kalvi 8th Maths Book Solutions Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 1 Rational Numbers Ex 1.2

Question 1.
Fill in the blanks:
(i) The multiplicative inverse of \(2 \frac{3}{5}\) is _____.
(ii) If -3 × \(\frac{6}{-11}=\frac{6}{-11}\) × x, then x is _______.
(iii) If distributive property is true for \(\left(\frac{3}{5} \times \frac{-4}{9}\right)+\left(x \times \frac{15}{17}\right)=\frac{3}{5} \times(y+z)\), then x, y, z are _____, _____ and ____.
(iv) If x × \(\frac{-55}{63}=\frac{-55}{63}\) × x = 1, then x is called the _____ of \(\frac{55}{63}\).
(v) The multiplicative inverse of -1 is ______.
Solution:
(i) \(\frac{5}{13}\)
(ii) -3
(iii) \(\frac{3}{5}, \frac{-4}{9}\) and \(\frac{15}{13}\)
(iv) Mulitplicative inverse
(v) -1

Question 2.
Say True or False.
(i) \(\frac{-7}{8} \times \frac{-23}{27}=\frac{-23}{27} \times \frac{-7}{8}\) illustrates the closure property of rational number.
(ii) Associative property is not true for subtraction of rational numbers.
(iii) The additive inverse of \(\frac{-11}{-17}\) is \(\frac{11}{17}\).
(iv) The product of two negative rational numbers is a positive rational number.
(v) The multiplicative inverse exists for all rational numbers.
Solution:
(i) False
(ii) True
(iii) False
(iv) True
(v) False

Question 3.
Verify the closure property for addition and multiplication of the rational numbers \(\frac{-5}{7}\) and \(\frac{8}{9}\)
Solution:
Closure property for addition.
Let a = \(\frac{-5}{7}\) and b = \(\frac{8}{9}\) be the given rational numbers.

∴ Closure property is true for addition of rational numbers.
Closure property for multiplication

∴ Closure property is true for multiplication of rational numbers.

Question 4.
Verify the associative property for addition and multiplication of the rational numbers \(\frac{-10}{11}, \frac{5}{6}, \frac{-4}{3}\).
Solution:


a × (b × c) = \(\frac{100}{99}\)
From (1) and (2) a × (b × c) = (a × b) × c is true for rational numbers.
Thus associative property is true for addition and multiplication of rational numbers.

Question 5.
Check the commutative property for addition and multiplication of the rational numbers \(\frac{-10}{11}\) and \(\frac{-8}{33}\).
Solution:
Let a = \(\frac{-10}{11}\) and b = \(\frac{-8}{33}\) be the given rational numbers.

From (1) and (2)
a + b = b + a and hence addition is commutative for rational numbers.

From (3) and (4) a × b = b × a
Hence multiplication is commutative for rational numbers.

Question 6.
Verify the distributive property a × (b + c) = (a × b) + (a × c) for the rational numbers a = \(\frac{-1}{2}\) ,b = \(\frac{2}{3}\) and c = \(\frac{-5}{6}\).
Solution:
Given the rational number a = \(\frac{-1}{2}\) ,b = \(\frac{2}{3}\) and c = \(\frac{-5}{6}\).

From (1) and (2) we have a × (b + c) = (a × b) + (a × c) is true.
Hence multiplication is distributive over addition for rational numbers Q.

Question 7.
Evaluate:

Solution:

Question 8.
Evaluate using appropriate properties.

Solution:

Question 9.
Use commutative and distributive properties to simplify \(\frac{4}{5} \times \frac{-3}{8}-\frac{3}{8} \times \frac{1}{4}+\frac{19}{20}\)
Solution:
Since multiplication is commutative

Objective Type Questions

Question 10.
Mulitplicative inverse of 0 (is)
(A) 0
(B) 1
(C) -1
(D) does not exist
Solution:
(D) does not exist

Question 11.
Which of the following illustrates the inverse property for addition?

Solution:
(A) \(\frac{1}{8}-\frac{1}{8}\) = 0

Question 12.
Closure property is not true for division of rational numbers because of the number
(A) 1
(B) -1
(C) 0
(D) \(\frac{1}{2}\)
Solution:
(C) 0

Question 13.
\(\frac{1}{2}-\left(\frac{3}{4}-\frac{5}{6}\right) \neq\left(\frac{1}{2}-\frac{3}{4}\right)-\frac{5}{6}\) illustrates that subtraction does not satisfy the ____ law of rational numbers.
(A) commutative
(B) closure
(C) distributive
(D) associative
Solution:
(D) associative

Question 14.
\(\left(1-\frac{1}{2}\right) \times\left(\frac{1}{2}-\frac{1}{4}\right) \div\left(\frac{3}{4}-\frac{1}{2}\right)\) = ______________

Solution:
(A) \(\frac{1}{2}\)

Students can Download Maths Chapter 5 Information Processing Additional Questions and Answers, Notes Pdf, Samacheer Kalvi 8th Maths Book Solutions Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 5 Information Processing Additional Questions

Additional Questions And Answers

Question 1.
A fast food restaurant has a meal special ?50 for a drink, sandwich, side item and dessert. The choices are Sandwich : Grilled chicken, All beef patty, Vegeburger and Fill filet.
Side : Regular fries, cheese fries, potato fries
Dessert: Chocolate chip cookie or Apple pie.
Drink: Fanta, Dr. Pepper, Coke, Diet coke and sprite.
How may meal combos are possible?
Solution:
There are 4 stages
1. Choosing a Sandwich
2. Choosing a side
3. Choosing a dessert
4. Choosing a drink
There are 4 different types of sandwich, 3 different types of side two different type of desserts and five different types of drink.
∴ The number of meal combos possible is = 4 × 3 × 2 × 5 = 120

Question 2.
A company puts a code on each different product they sell. The code is made up of 3 numbers and 2 letters. How many different codes are possible?
Solution:
There are 5 stages, Number – 1
Number – 2
Number – 3
Letter – 1
Letter – 2
There are 10 possible numbers 0 to 9
There are 26 possible letters A to Z.
We have 10 × 10 × 10 × 26 × 26 = 6,76, 000 possible codes.

Question 3.
Rani take a survey with five ‘yes’ or ‘No’ answers. How many different ways could she complete the survey?
Solution:
There are 5 stages
Question – 1
Question – 2
Question – 3
Question – 4
Question – 5
There are 2 choices for each question (Yes/No)
∴ Total number of possible ways to answer
= 2 × 2 × 2 × 2 × 2 = 32 ways.

Question 4.
There are 2 vegetarian entry options and 5 meat entry options on a dinner menu. What number of ways one can opt a dinner for any one of it?
Solution:
Number of veg options = 2
Number of meat option = 5
One can opt for any one dinner
∴ Total number of ways = 2 + 5 = 7 ways

Additional Questions And Answers

Question 1.
Colour the graph with minimum number of colours and no two adjacent vertices should have the same colour.
Solution:

Test Yourself

Question 1.
You have three dice, How many possible out comes are there on a toss?
Solution:
8

Question 2.
Your school offers tow English classes three maths classes and 3 history classes, you want to take one of each class. How many different ways are there to organize your schedule?
Solution:
18

Question 3.
A wedding caterer gives 3 choices for main dish, sin starters, five dessert. How many different meals (made up of starter, dinner and dessert and are there?
Solution:
90

Question 4.
In a company ID cards have 5 digit numbers.
(a) How many ID cards can he formed if repetition of the digits allowed?
(b) How many ID cards can be formed if repetition of digits is not allowed?
Solution:
(i) 10,000
(ii) 30,240

Question 5.
A student is shopping for a new computer. He is deciding among 3 desktop and 4 laptop computer. How many ways she can buy a computer?
Solution:
7

Question 6.
Colour the vertices bear the same colour using minimum number of colours.

Students can Download Maths Chapter 1 Rational Numbers Ex 1.1 Questions and Answers, Notes Pdf, Samacheer Kalvi 8th Maths Book Solutions Guide Pdf helps you to revise the complete Tamilnadu State Board New Syllabus and score more marks in your examinations.

Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 1 Rational Numbers Ex 1.1

Question 1.
Fill in the blanks:
(i) \(\frac{-19}{5}\) lies between the integers _____ and _____
(ii) The rational number that is represented by 0.44 is ______.
(iii) The standard form of \(\frac{+58}{-78}\) is _____.
(iv) The value of \(\frac{-5}{12}+\frac{7}{15}\) = ______
(v) The value of \(\left(\frac{-15}{23}\right) \div\left(\frac{+30}{-46}\right)\) is ______
Solution:
(i) -4 and -3
(ii) \(\frac{11}{25}\)
(iii) \(\frac{-29}{39}\)
(iv) \(\frac{1}{20}\)
(v) 1

Question 2.
Say True or False.
(i) 0 is the smallest rational number.
(ii) There are an unlimited rationals between 0 and 1.
(iii) The rational number that does not have a reciprocal is 0.
(iv) The only rational number which is its own reciprocal is -1.
(v) The rational numbers that are equal to their additive inverses are 0 and -1.
Solution:
(i) False
(ii) True
(iii) True
(iv) False
(v) False

Question 3.
List five rational numbers between 2 and 0
(i) -2 and 0
(ii) \(\frac{-1}{2}\) and \(\frac{3}{5}\)
(iii) 0.25 and 0.35
(iv) -1.2 and -2.3
Solution:
(i) -2 and 0

Question 4.
Write four rational numbers equivalent to -3 7
(i) \(\frac{-3}{5}\)
(ii) \(\frac{7}{-6}\)
(iii) \(\frac{8}{9}\)
Solution:

Question 5.
Draw the number line and represent the following rational numbers on it.

Solution:

Question 6.
Find the rational numbers for the points marked on the number line.

Solution:
(i) The number lies between -3 and -4. The unit part between -3 and -4 is divided into 3 equal parts and the second part is asked.
∴ The required number is \(-3 \frac{2}{3}=-\frac{11}{3}\).
(ii) The required number lies between 0 and -1. The unit part between 0 and -1 is divided into 5 equal parts, and the second part is taken.
∴The required number is \(-\frac{2}{5}\)
(iii) The required number lies between 1 and 2. The unit part between 1 and 2 is divided into 4 equal parts and the third part is taken.
∴ The required number is \(1 \frac{3}{4}=\frac{7}{4}\)

Question 7.
Using average, write 3 rational numbers between \(\frac{14}{5}\) and \(\frac{16}{3}\)
Solution:

Question 8.
Verify that -(-x) is the same x for:
(i) x = \(\frac{11}{15}\)
(ii) x = \(\frac{-31}{45}\)
Solution:

Question 9.
Re-arrange suitable and add :
\(\frac{-3}{7}+\frac{5}{6}+\frac{4}{7}+\frac{1}{3}+\frac{13}{-6}\)
Solution:

Question 10.
What should be added to \(\frac{-8}{9}\) to get \(\frac{2}{5}\).
Solution:
Let the number to be added = x

Question 11.
Subtract \(\frac{-8}{44}\) from \(\frac{-17}{11}\)
Solution:

Question 12.
Evaluate:
(i) \(\frac{9}{2} \times \frac{-11}{3}\)
(ii) \(\frac{-7}{27} \times \frac{24}{-35}\)
Solution:

Question 13.
Divide
(i) \(\frac{-21}{5}\) by \(\frac{-7}{-10}\)
(ii) \(\frac{-3}{13}\) by -3
(iii) -2 by \(\frac{-6}{15}\)
Solution:

Question 14.
Simplify \(\left(\frac{2}{5}+\frac{3}{2}\right)+\frac{3}{10}\) as a rational number and show that it is between 6 and 7.
Solution:

Question 15.
Write the five rational numbers which are less than -2.
Solution:
All the integers are rational numbers
∴ Rational numbers less than -2 are -10, -15, -20, -25, -30

Question 16.
Compare the following pairs of rational numbers

Solution:


\(\frac{10}{15}<\frac{12}{15}\)
∴ \(\frac{2}{3}<\frac{4}{5}\)

Question 17.
Arrange the following rational numbers is ascending and descending order.

Solution:

Objective Type Questions

Question 18.
The number which is subtracted from \(\frac{-6}{11}\) to get \(\frac{8}{9}\) is

Solution:
(B) \(\frac{-142}{99}\)
Hint:
Let x be the number be subtracted

Question 19.
Which of the following rational numbers is the greatest?

Solution:
(A) \(\frac{-17}{24}\)
Hint:
LCM of 24, 16, 8, 32 = 8 × 2 × 3 × 2 = 96


∴ \(\frac{-17}{24}\) is the greatest number.

Question 20.
\(\frac{-5}{4}\) is a rational number which lies between
(A) 0 and \(\frac{-5}{4}\)
(B) -1 and 0
(C) -1 and -2
(D) -4 and -5
Solution:
(C) -1 and -2
Hint:
\(\frac{-5}{4}\) = \(-1 \frac{1}{4}\)
∴ \(\frac{-5}{4}\) lies between -1 and -2.

Question 21.
The standard form of \(\frac{3}{4}+\frac{5}{6}+\left(\frac{-7}{12}\right)\) is

Solution:
(D) 1
Hint:

Question 22.
The sum of the digits of the denominator in the simplest form of \(\frac{112}{528}\)
(A) 4
(B) 5
(C) 6
(D) 7
Solution:
(C) 6
Hint:

Sum of digits in the denominator = 3 + 3 = 6

Question 23.
The rational number (numbers) which has (have) additive inverses is (are)
(A) 7
(B) \(\frac{-5}{7}\)
(C) 0
(D) all of these
Solution:
(D) all of these
Hint:
Additive inverse of 7 is -7
Additive inverse of \(\frac{-5}{7}\) is \(\frac{-5}{7}\)
Additive inverse of 0 is 0.

Question 24.
Which of the following pairs is equivalent?

Solution:
(B) \(\frac{16}{-30}, \frac{-8}{15}\)
Hint:

∴ \(\frac{16}{-30}\) and \(\frac{8}{15}\) are equivalent fraction.

Question 25.
\(\frac{3}{4} \div\left(\frac{5}{8}+\frac{1}{2}\right)\) =

Solution:
(C) \(\frac{2}{3}\)
Hint:

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Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 5 Information Processing Ex 5.3

MISCELLANEOUS QUESTIONS

Question 1.
Shanthi has 5 chudithar sets and 4 Frocks. In how many possible ways, can she wear either a chudithar or a frock ?
Solution:
Shanthi his 5 chudidhar sets and 4 frocks.
She wear either chudidhar or a frock.
∴ Total possible ways = 5 + 4 = 9 ways

Question 2.
In a Higher Secondary School, the following types of groups are available in XI standard
I. Science Group:
(i) Physics, Chemistry, Biology and Mathematics
(ii) Physics, Chemistry, Mathematics and Computer Science
(iii) Physics, Chemistry, Biology and Home Science
II. Arts Group:
(i) 1. Accountancy, Commerce, Economics and Business Maths
(ii) 2. Accountancy, Commerce, Economics and Computer Science
(iii) 3. History, Geography, Economics and Commerce
III. Vocational Group:
(i) Nursing – Biology, Theory, Practical I and Practical II
(ii) Textiles and Dress Designing – Home Science, Theory, Practical I and Practical II
In how many possible ways, can a student choose the group?
Solution:
The student either select any one of science group in 3 ways or any of the arts group in 3 ways or any of the vocational group in 2 ways.
∴ Total possible ways = 3 + 3 + 2 = 8 ways

Question 3.
An examination paper has 3 sections, each with five instructed to answer one question from each section. In can the questions be answered?
Solution:
The tree diagram for this may be

∴ Number of possible ways to select one questions from each of 3 sections is 3 × 5 = 15 ways.

Question 4.
On a sports day, students must take also part in one of the one track events 100m Running and 4 × 100 m Relay. He must take part of any of the field events Long Jump, High Jump and Javelin Throw. In how many different ways can the student take part in the given events?
Solution:
Number of track events ⇒ (100m running, 4 × 100 m Relay) 2.
Number of field events ⇒ (Long jump, High jump, Javelin Throw) 3.
Students can take part in the given events in 2 × 3 = 6 ways.

Question 5.
The given spinner is spun twice and the two numbers got are used to form a 2 digit number. How many different 2 digits numbers are possible?

Solution:
On the first spin we get any of the five numbers to form ones place then insecond spin the number got will fill 10’s place.
∴ Number of ways = 5 × 5 = 25 ways.
Removing the repetitions (11, 22, 33, 44, 55) once we get 25 – 5 = 20 ways.
20 different two digit numbers are possbile

Question 6.
Colour the following pattern with as few colours as possible but make sure that no two adjacent sections are of the same colour.

Solution:

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Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 1 Rational Numbers Additional Questions

Additional Questions And Answers

Exercise 1.1

Very Short Answers [2 Marks]
Question 1.
Add \(\frac{3}{5}\) and \(\frac{13}{5}\)
Solution:

Question 2.
Add \(\frac{7}{9}\) and \(\frac{-12}{9}\)
Solution:

Question 3.
Add \(\frac{-3}{7}\) and \(\frac{-17}{7}\)
Solution:

Question 4.
Add \(\frac{4}{-13}\) and \(\frac{7}{13}\)
Solution:

Question 5.
Subtract \(\frac{3}{4}\) and \(\frac{7}{4}\)
Solution:
\(\frac{7}{4}-\frac{3}{4}=\frac{7-3}{4}=\frac{4}{4}\) = 1

Short Answers [3 Marks]

Question 1.
Add \(\frac{4}{-3}\) and \(\frac{8}{15}\)
Solution:

Question 2.
Simplify \(\frac{9}{-27}+\frac{18}{39}\)
Solution:

Long Answers [5 Marks]

Question 1.
By what number should we multiply \(\frac{3}{-14}\), so that the product may be \(\frac{5}{12}\)
Solution:
Let the number to be multiplied by x

∴ The number to be multiplied = \(\frac{-35}{18}\)

Question 2.
Simplify

Solution:

Exercise 1.2

Very Short Answers [2 Marks]
Question 1.
Verify addition of rational number is closed using \(\frac{1}{4}\) and \(\frac{2}{3}\)
Solution:

∴ Addition of rational numbers is closed

Question 2.
Is subtraction is commutative for rational numbers. Given an example.
Solution:
No, subtraction is not commutative for rational numbers.
Example: Let a = \(\frac{1}{2}\) and b = \(\frac{5}{6}\)

From (1) and (2)
a – b ≠ b – a for rational numbers

Very Short Answers [5 Marks]

Question 1.
Verify associative property for addition of rational numbers for a = \(\frac{5}{6}\), b = \(\frac{-3}{4}\), c = \(\frac{4}{7}\)
Solution:
Given a = \(\frac{5}{6}\), b = \(\frac{-3}{4}\), c = \(\frac{4}{7}\)

From (1) and (2) we have (a + b) + c = a + (b + c)
∴ Associative property is true for addition of rational numbers.

Question 2.
Verify distributive property of multiplication over addition for the rational numbers a = \(\frac{3}{4}\), b = \(\frac{-2}{3}\), c = \(\frac{3}{7}\)
Solution:
Given a = \(\frac{3}{4}\), b = \(\frac{-2}{3}\), c = \(\frac{3}{7}\)
To verify a × (b + c) = (a × b) + (a × c)


From (1) and (2)
a × (b + c) = (a × b) + (a × c)
∴ Distributive property of multiplication over addition is true for the given rational numbers.

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Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 5 Information Processing Ex 5.2

Question 1.
Colour the following patterns with as few colours as possible but make sure that no two adjacent sections are of the same colour.
Solution:

Question 2.
Ramya wants to paint a pattern in her living room wall with a minimum budget. Help her to colour the pattern with 2 colours but make sure that no two adjacent boxes are the same colour. The pattern is shown in the picture.

Solution:

Question 3.
Colour the countries in the following maps with as few colours as possible but make
sure that no two adjacent countries are of the same colour.

Solution:

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Tamilnadu Samacheer Kalvi 8th Maths Solutions Term 1 Chapter 4 Geometry Ex 4.1

Question 1.
From the figure given, prove that ∆ABC ~ ∆DEF.

Solution:
From the ∆ABC,
AB = AC
It is an isosceles triangle
Angles opposite to equal sides are equal
∴ ∠B = ∠C = 65°
∴ ∠B + ∠C = 65° + 65°
= 130°
We know that .sum of three angles is a triangle = 180°
∠A + ∠B + ∠C = 180°
∠A + 130° = 180°
∠A = 180°-130°
∠A = 50°
From ∆DEF, ∠D = 50°
∴ Sum of Remaining angles = 180° – 50° = 130°
DE = FD
∴ ∠D = ∠F
From ∆ABC and ∆DEF

∠A = ∠D = 50°
∠B = ∠E = 65°
∠C = ∠F = 65°
∴ By AAA criteria ∆DEF ~ ∆ABC

Question 2.
Prove that ∆GUM ~ ∆ BOX from the given figure.

Solution:


That is their corresponding sides are proportional.
∴ By SSS similarity ∆GUM ~ ∆BOX.

Question 3.
In the given figure YH ||TE Prove that ∆WHY ~ ∆WET and also find HE and TE.

Solution:

Question 4.
In the given figure, if ∆EAT ~ ∆BUN find the measure of all angles.

Solution:
Given ∆EAT ≡ ∆BUN
∴ Corresponding angles are equal
∴ ∠E = ∠B ..(1)
∠A = ∠U ..(2)
∠T = ∠N ..(3)
∠E = x°
∠A = 2x°
Sum of three angles of a triangle = 180°
In ∆EAT, x + 2x + ∠T = 180°
∠T = 180° – (x° + 2x° )
∠T = 180°- 3x° …(4)
Also in ∆BUN
(x + 40)° + + ∠U = 180°
x + 40° + x + ∠U = 180°
2x° + 40° + ∠U = 180°
∠U = 180° – 2x – 40°
= 140° – 2x°
Now by (2)
∠A = ∠U
2x = 140° – 2x
2x + 2x = 140°
4x = 140°

∠A = 2x° = 2 × 35° = 70°
∠N = x + 40°
= 35° + 40° = 75°
∴ ∠T = ∠N = 75°
∠E = ∠B = 35°
∠A = ∠U = 70°

Question 5.
From the given figure, UB || AT and CU ≡ CB Prove that ∆CUB ~ ∆CAT and hence ∆CAT is isosceles.

Solution:

Question 6.
In the figure, ∠CIP ≡ ∠COP and ∠HIP ≡ ∠HOP. Prove that IP ≡ OP.

Solution:

Question 7.
In the given triangle, AC ≡ AD and ∠CBD ≡ ∠DEC. Prove that ∆BCF ≡ ∆EDF.

Solution:

Question 8.
In the given figure, ∆ BCD is isosceles with base BD and ∠BAE ≡ ∠DEA. Prove that AB ≡ ED .

Solution:

Question 9.
In the given figure, D is the midpoint of OE and ∠CDE = 90°. Prove that ∆ODC ≡ ∆EDC.

Solution:

Question 10.
In the figure, if SW ≡ SE and ∠NWO ≡ ∠NEO. then, prove that NS bisects WE and ∠NOW = 90°

Proof:

Question 11.
Is ∆PRQ ≡ ∆QSP ? Why ?

Solution:
In ∠PRQ = ∠PSQ = 90° given
PR = QS = 3 cm given
PQ = PQ = 5 cm common
It satisfies RHS criteria
∴ ∆PRQ congruent to ∆QSP.

Question 12.
Fill in the blanks with the most correct term from the given list.
(in proportion, similar, corresponding, congruent shape, area, equal)
Statements Reasons

Question 1.
Corresponding sides of similar triangles are ___.
Solution:
in proportion

Question 2.
Similar triangles have the same ___ but not necessarily the same size.
Solution:
shape

Question 3.
In similar triangles, ___ sides are opposite to equal angles.
Solution:
equal

Question 4.
The symbol ~ is used to represent ___ triangles.
Solution:
congruent

Question 5.
The symbol ~ is used to represent ____ triangles.
Solution:
similar

Objective Type Questions

Question 13.
Two similar triangles will always have ___ angles
(A) acute
(B) obtuse
(C) right
(D) matching
Solution:
(D) matching

Question 14.
If in triangles PQR and XYZ, \(\frac{P Q}{X Y}=\frac{Q R}{Z X}\) then they will be similar if
Solution:
(C) Q = ∠X

Question 15.
A flag pole 15 cm high casts a shadow of 3 m at 10 a.m. The shadow cast by a building at the same time is 18.6 m. The height of the building is
(A) 90 m
(B) 91 m
(C) 92 m
(D) 93 m
Solution:
(D) 93 m

Question 16.
If ∆ABC ~ ∆PQR in which ∠A = 53° and ∠Q = 77°, then ∠R is
(A) 50°
(B) 60°
(C) 70°
(D) 80°
Solution:
(A) 50°

Question 17.
In the figure, which of the following statements is true?
(A) AB = BD
(B) BD < CD
(C) AC = CD
(D) BC = CD

Solution:
(C) AC = CD