CBSE Important Questions for class 8 Maths chapter Rational Numbers
Important Questions for CBSE Class 8 Maths
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Short Answer Type Questions

Q1. What are the multiplicative and additive identities of rational numbers?

Ans. 0 and 1 are rational numbers' additive and multiplicative identities.

Q2. Write the additive inverse of 19/6 and 2/3

Ans. 19/6 = 19/6 and ⅔ = 2/3

Q3. Write the multiplicative inverse of 13/19 and 7

Ans. 13/19 = 19/13 and 7 = 1/7

Q4. Mention a rational number that has no reciprocal.

Ans. A rational number “0” has no reciprocal or multiplicative inverse.

Q5. Mention any 4 rational numbers which are less than 5.

Ans. 1, 1, 2 and 3.
Long Answer Type Questions

Q6. Mention the commutativity, associative and distributive properties of rational numbers. Also, check a × b = b × a and a + b = b + a for a = 1/2 and b = 3/4

Ans. Commutative property:

For any two rational numbers, a and b, a + b = b + a.

For any two rational numbers, a and b, a × b = b × a.

Associative Property:

For any three rational numbers a, b and c,

(a + b) + c = a + (b + c)

Distributive property states that for any three numbers x, y and z,

x × ( y + z ) = (x × y) + ( x × z)

a x b = b x a

a x b = 1/2 x 3/4 = 3/8

b x a = 3/4 x 1/2 = 3/8

a + b = 3/4 + 1/2 = 5/4

b + a = 1/2 + 3/4= 5/4

Q7. Write any 5 rational numbers between −2/5 and ½.

Ans. −2/5 can be written as −8/20.

1/2 can be written as 10/20.

So, rational numbers between these two numbers can be,

−7/20,−6/20,−5/20,−4/20,−3/20,−2/20,−1/20,0,1/20,2/20,3/20,4/20.

Q8. If the product of any two rational numbers is two and one is 1/7, find the other?

Ans. Consider two rational numbers: "a" and "b."

Given, a = 1/7 and a × b = 2

Now, 1/7 × b = 2

b = 7 × 2 = 14

So, the other rational number will be 14.

Q9. Mr. X went shopping with a certain amount of money. He spent Rs. 10(¼) on buying a pen and Rs. 25(¾) in food. He then gave the remaining Rs. 16(½) to his friend. Calculate how much money he initially had.

Ans. To get the amount of money Mr. X initially had, his purchases must be added.

So,

Initial Money = 10(¼) + 25(¾) + 16(½)

= 41/4 + 103/4 + 33/2

By taking LCM, we get

Initial Money = 105/2
Find below Important Questions for class 8 Maths chapter 1 Rational Numbers