Important Questions for Class 8 Chapter 1-Rational Numbers

Are you in class 8th? Did you start preparing for your Maths exam now? Don’t worry. If you are preparing for your final exam or any other test, you can use this free set of important questions for CBSE class 8th Maths PDF for practice.

Important questions based on NCERT syllabus for Class 7 Chapter 1 - Rational Numbers:

Question 1: What number should be added to −7/8 so as to get 5/9?
Solution: We have,
Given number =−7/8
The sum of the given number and the required number =5/9
∴ Required number = sum of the numbers - given number
=5/9−(−7/8)
=5/9+7/8
=40+63/72
=103/72
The required number =103/72

Question 2: Simplify the following
1/12+(−5/18)−7/24
Solution:
We have 1/12+(−5/18)−7/24 = 1/12−5/18−7/24
LCM of 12, 18 and 24 is 72
= 6/72−20/72−21/72
= 6−20−21/72
= 6−41/72
= −35/72
Which is the required answer.

Question 3: By what numbers should −15/28 be multiplied, so that the product may be −5/7?
Solution: We have,
Product of two numbers =−15/28
one of the numbers =−5/7
∴ The other number = product of the numbers ÷ given number
= −5/7÷(−15/28)=−5/7×28/−15
= (−5)×28/ 7×(−15)
= 1×4/1×3
= 4/3

Question 4: On one day a rickshaw puller earned Rs.80. Out of his earnings he spent Rs.133/5 on tea and snacks, Rs.12 1/2 on food and Rs.4(2/5) on repairs of the rickshaw. How much did he save on that day?
Solution:
His savings = His earning - total expenditure
His savings = 80 − (13 3/5 + 12 ½ + 4 (2/5))
= 80 − (68/5 + 2/52 + 2/25)
= 80 − (136 + 125 + 44)/10
= 80 – 305/10
= (800 − 305)/10
= 495/10
= 49(5/10)
His savings = 49 ½

Question 5: If 3/5 of a number exceeds its 2/7 by 44, find the number.
Solution:
Let the number be x
then 3/5 of a number = (3/5)x
2/7 of a number = (2/7)x
Then, (3/5)x – (2/7)x = 44
3x/5 −2x/ 7 = 44
(21x−10x)/35 = 44
11x = 44×35
x = (44×35)/11
x = 140