Mathematics Questions - Class 8

Question 1

Which of the following equations led to the need for rational numbers?

Accepted Answer

2x = 3

Answer

x + 2 = 13

Answer

x + 5 = 5

Answer

x + 18 = 5

Question 2

A rational number is defined as a number that can be written in the form p/q where:

Accepted Answer

p and q are integers and q ≠ 0

Answer

p and q are natural numbers

Answer

p and q are whole numbers and q ≠ 0

Answer

p and q are positive integers

Question 3

Which number system is closed under all four basic operations (addition, subtraction, multiplication, division)?

Accepted Answer

None of the above

Answer

Natural numbers

Answer

Whole numbers

Answer

Integers

Question 4

What is the result of 3/8 + (-5/7)?

Accepted Answer

-19/56

Answer

19/56

Answer

-2/15

Answer

8/15

Question 5

Which property is demonstrated by: 2/3 × 4/5 = 4/5 × 2/3?

Accepted Answer

Commutative property

Answer

Associative property

Answer

Distributive property

Answer

Identity property

Question 6

Subtraction is NOT commutative for rational numbers. Which example proves this?

Accepted Answer

2/3 - 5/4 ≠ 5/4 - 2/3

Answer

2/3 - 5/4 = 5/4 - 2/3

Answer

2/3 + 5/4 = 5/4 + 2/3

Answer

2/3 × 5/4 = 5/4 × 2/3

Question 7

The associative property for addition states that:

Accepted Answer

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

Answer

a + b = b + a

Answer

a + 0 = a

Answer

a(b + c) = ab + ac

Question 8

What is the additive identity for rational numbers?

Accepted Answer

0

Answer

1

Answer

-1

Answer

1/2

Question 9

What is the multiplicative identity for rational numbers?

Accepted Answer

1

Answer

0

Answer

-1

Answer

Any rational number

Question 10

The distributive property of multiplication over addition is written as:

Accepted Answer

a × (b + c) = (a × b) + (a × c)

Answer

a + (b × c) = (a + b) × (a + c)

Answer

(a × b) + c = a × (b + c)

Answer

a × b × c = (a × b) × c

Question 11

Calculate: (-7/3) × (6/5) × (-14/9)

Accepted Answer

28/9

Answer

-28/9

Answer

196/135

Answer

-196/135

Question 12

Which property allows us to compute (1/3 × 4/3) × 1/3 as 1/3 × (4/3 × 1/3)?

Accepted Answer

Associative property

Answer

Commutative property

Answer

Distributive property

Answer

Identity property

Question 13

Are whole numbers closed under subtraction?

Accepted Answer

No, because 5 - 7 = -2 is not a whole number

Answer

Yes, always

Answer

Yes, but only for positive results

Answer

Only when the first number is larger

Question 14

Solve using distributivity: 7/5 × (3/12 - 5/12)

Accepted Answer

-7/30

Answer

7/30

Answer

-2/15

Answer

2/15

Question 15

What makes rational numbers different from integers?

Accepted Answer

Rational numbers can be expressed as fractions p/q where q ≠ 0

Answer

Rational numbers include negative numbers

Answer

Rational numbers are always positive

Answer

Integers are larger than rational numbers

Question 16

If 2/5 + x = 2/5, what is the value of x?

Accepted Answer

0

Answer

1

Answer

2/5

Answer

-2/5

Question 17

Calculate: 3/7 + 6/11 + 8/21 + 5/22 using properties efficiently

Accepted Answer

Group as (3/7 + 8/21) + (6/11 + 5/22)

Answer

Add all numerators and denominators separately

Answer

Convert all to the same denominator first

Answer

Use only commutativity

Question 18

Why are rational numbers NOT closed under division?

Accepted Answer

Division by zero is undefined

Answer

Division always gives irrational results

Answer

Division of fractions is too complicated

Answer

Division gives negative results

Question 19

Which operation is both commutative and associative for rational numbers?

Accepted Answer

Addition and multiplication

Answer

Subtraction only

Answer

Division only

Answer

All four operations

Question 20

Evaluate: (-4/5) × (3/7) × (15/16) × (-14/9)

Accepted Answer

1/2

Answer

-1/2

Answer

2

Answer

-2

Mathematics Class 8

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