Class 8th Mathematics MCQ

Q70. The side of a cube is 2a. Find the volume of the cube.

1. 8

2. 8a

3. 4a

4. 2a

Ans: 2. 8a

Solution:

Volume of the cube = 2a × 2a × 2a = 8a

Q71. What should be added to 9y -7xyz + 8z – xy to get 3xy + 8zy – 2xyz + z we get:

1. -9y + 4xy + 8zy + 5xyz + z – 8z

2. 9y + 4xy + 8yz + 5xyz + z + 8z

3. 9y + 4xy + 8zy + 5xyz + z – 8z

4. None of these

Ans: 1. -9y + 4xy + 8zy + 5xyz + z – 8z

Solution:

Subtracting 9y – 7xyz + 8z – xy from 3xy + 8zy – 2xyz + z , we ge

Q72. The value of x – 2yx + y when x = 1, y = 2 is:

1. 1

2. -1

3. 2

4. -2

Ans: 1. 1

Solution:

Value = (1) – 2(2)(1) + (2) = 1

Q73. Use suitable identity to evaluate 992.

1. 9801

2. 10199

3. 10201

4. 10001

Ans: 1. 9801

Q74. (a – b) is equal to: 

1. a + b + 2ab

2. 2ab

3. a + b – 2ab

4. a + ba

Ans: 3. a + b – 2ab

Solution:

By algebraic identity,

(a + b) = a + b – 2ab

Q75. The value of (3x + 9x + 27x) ÷ 3x is:

1. x + 9 + 27x

2. 3x + 3x + 27x

3. 3x + 9x + 9

4. x + 3x + 9

Ans: 4. x + 3x + 9

Solution:

(3×2 + 9×2 + 27x)

=

3×3 + 9×2 + 27x

3x

=

3×3

3x +

9×2

3x +

27x

3x

= x2 + 3x + 9

Q76. Tick (✓ ) the correct answer:

(3q + 7p – 2r + 4) – (4p – 2q + 7r – 3) = ?

1. (p + 2q + 5r + 1)

2. (11p + q + 5r + 1)

3. (-3p – 5q + 9r – 7)

4. (3p + 5q – 9r +7)

Ans: 4. (3p + 5q – 9r +7)

Solution:

(3q + 7p – 2r + 4) – (4p – 2q + 7r – 3)

= 3q + 7p – 2r + 4 – 4p + 2q – 7r + 3

= 5q + 3p – 9r + 7

= 3p + 5q – 9r + 7

Q77. Which of the following is a binomial?

1. 3xy

2. 4l + 5m

3. 2x + 3y – 5

4. 4a – 7ab + 3b + 12

Ans: 2. 4l + 5m

Solution:

4l + 5m contains two terms.

Q78. Evaluate (199.5) using a suitable identity.

1. 400200.25

2. 39800.025

3. 39800.25

4. 39800

Ans: 3. 39800.25

Solution:

(199.5) = (200 – 0.5) and using (a – b) = a – 2ab + b = (200) – 2 × 200 × 0.5 + (0.5) = 40000 – 200 + 0.25 = 39800.25

Q79. The result of subtraction of 7x from 0 is: 

1. 0

2. 7x

3. -7x

4. x

Ans: 3. -7x

Solution:

0 – 7x = -7x

Q80. Which of the following is not binomial:

1. M + n

2. Mn

3. M – n

4. M2 – n2

Ans: 2. Mn

Q81. Surbhi tries o make one of the first three identities from (x + a)(x + b) = x + (a + b)x + ab by replacing a and b both

by – c which identity did she obtain by this?

1. (a – b) = a – 2av + b

2. (a – b) = a – 2ab + b

3. a – b = (a + b)(a – b)

4. (x + a)(x + b) = x – (a + b) x + ab remains same

Ans: 2. (a – b) = a – 2ab + b

Solution:

(x + a)(x + b) = x + (a + b) x + ab

Replacing a and b both by – c, we get

(x – c)(x – c) = x + (-c -c) x + (-c) (-c)

Or, (x – c)2 = x – 2 cx + c

It is similar to

(a – b) = a – 2ab + b

Q82. Which of the following is a binomial?

1. 7 × a + a

2. 6a + 7b + 2c

3. 4a × 3b × 2c

4. 6 (a + b)

Ans: 4. 6 (a + b)

Solution:

Binomials are algebraic consisting of two unlike terms.

1. 7 × a + a = 7a + a = 8a (monomial)

2. 6a + 7b + 2c (trinomial)

3. 4a × 3b × 2c (monomial)

4. 6(a + b) = 6a + 6b (binomial)

Q83. What is the formulae for (x – y) ?

1. x + 2xy + y

2. x – 2xy + y

3. x – 2xy – y

4. x – y

Ans: 2. x – 2xy + y

Q84. The product of 4x and 0 is:

1. 4

2. 0

3. 4x

4. None of the above

Ans: 2. 0

Solution:

Any value multiplied by zero is zero.

Q85. ‘2’ is common factor of the expressions

1. 12a b, 15ab

2. 5xy, 10x

3. 10x , -18x , 14x

4. 33y, -22z

Ans: 3. 10x , -18x , 14x

Q86. Factorised form of p – 17p – 38 is:

1. (p – 19)(p + 2)

2. (p – 19)(p – 2)

3. (p + 19)(p + 2)

4. (p + 19)(p – 2)

Ans: 1. (p – 19)(p + 2)

Solution:

We have,

p – 17p – 38

= p – 19p + 2p – 38

= p(p – 19) + 2(p – 19)

= (p – 19)(p + 2)

Q87. The value of x – 2x + 1 when x = 1 is:

1. 1

2. 2

3. -2

4. 0

Ans: 4. 0

Solution:

Value = (1) – 2(1) + 1 = 0

Q88. If a+b + c = 10 and a2 + b2 + c2 = 36 then ab+bc + ca = ________

1. 136

2. 64

3. 32

4. 68

Ans: 3. 32

Q89. Which of the following is a monomial?

1. 4x

2. a + 6

3. a + 6 + c

4. a + b + c + d

Ans: 1. 4x

Solution:

4x contains only one term.

Q90. What do you get when you subtract -3xy from 5xy?

1. 3xy

2. 5xy

3. 8xy

4. xy

Ans: 3. 8xy

Solution:

5xy – (-3xy) = 5xy + 3xy = 8xy

Q91. The product of 3xy z and 4x is:

1. 12x yz

2. 12xy

3. 12xyz

4. 12x y z

Ans: 4. 12x y z

Solution:

The product of 3xy z and 4x is:

⇒ (3xy z) (4x)

⇒ 3.x.y .z.4.x

⇒ 12x y z

Q92. If the product of two numbers is 10 and the sum is 7, then the larger of the two numbers is:

1. -2

2. 5

3. 2

4. None of these

Ans: 2. 5

Q93. (3x – 5y) – (5x – 2y) + (2x + 3y)

1. -3(3x – 5y)(2x – 5y)(2x + 3y)

2. 3(3x – 5y)(5x – 2y)(2x + 3y)

3. (3x – 5y)(2y – 5x)(2x + 3y)

4. (3x – 5y)(5x – 2y)(2x + 3y)

Ans: 1. -3(3x – 5y)(2x – 5y)(2x + 3y)

Q94. What is the volume of a cube having side (3ab)cm :

1. (27a b )cm

2. (9ab)cm

3. (27ab)cm

4. (9a b )cm

Ans: 1. (27a b )cm

Solution:

The volume of a cube having side 3ab = (3ab) × (3ab) × (3ab) = 3 × 3 × 3 (ab) (ab) (ab) = (27a b )cm

Q95. The product of 7x and -12x is:

1. 84x

2. -84x

3. x

4. -x

Ans: 2. -84x

Solution:

(7x)(-12x) = -84x

Q96. The equality b + 5 > 9b + 12 us satisfied if:

1. b > 8 (or) b < 0

2. b = 10 (or) b = –1

3. b > 9 (or) b < 0

4. b > 9 (or) b < 1

Ans: 3. b > 9 (or) b < 0

Q97. The number of like terms in abc, – abc, – bca, acb, bac,

1

2 12cab is:

1. 6

2. 4

3. 3

4. 2

Ans: 1. 6

Solution:

All are like terms

Q98. What are added together to form an expression?

1. Factors

2. Terms

3. Coefficients

4. Variables

Ans: 2. Terms

Solution:

The correct option (B) because expressions are formed by adding terms together.

Q99. Product of the following monomials 4p, -7q , -7pq is:

1. 196 p q

2. 196 pq

3. -196 p q

4. 196 p q

Ans: 1. 196 p q

Solution:

Required Product = 4p × (-7q ) × (-7pq)

= 4 × (-7) × (-7)p × q × pq

= 196p q

Q100. Simplify 7pq(q + r) – 8s(p + 2q) + 2r(pq + rs) + 4ps:

1. 7pq + 9pqr + 4ps + 16qs + 2r s

2. 7pq + 5pqr – 4ps + 16qs + 2r s

3. 7pq + 9pqr – 4ps – 16qs + 2r s

4. 7pq – 5pqr + 4ps – 16qs + 2r s

Ans: 3. 7pq + 9pqr – 4ps – 16qs + 2r s

Solution:

7pq(q + r) – 8s(p + 2q) + 2r(pq + rs) + 4ps = 7pq (q) + 7pq(r) – 8s(p)-

8s(2q) + 2r(pq) + 2r(rs) + 4ps

7pq + 7pq(r) – 8ps – 16qs + 2pqr + 2r s + 4ps 7pq + 9pqr – 8ps – 4ps – 16qs + 2r

Q101. Which of the following expression is trinomial:

1. xyz

2. xy + z

3. x + y + z

4. x + yz

Ans: 3. x + y + z

Q102. The common factor of 3ab and 2cd is:

1. 1

2. -1

3. a

4. c

Ans: 1. 1

Solution:

We have, monomials 3ab and 2cd Now, 3ab = 3 × a × b and 2cd = 2 × c × d Observing the monomials, we see that, there is no common

factor (neither numerical nor literal) between them except 1.

Q103. The value of (x – y)(x + y) + (y – z)(y + z) + (z – x)(z + x) is:

1. 0

2. x + y + z

3. x + y + z

4. xy + yz + zx

Ans: 1. 0

Solution:

(x – y)(x + y) + (y – z)(y + z) + (z – x)(z + x)

= x – y + y – z + z – x

[By algebraic identity: a – b = (a + b)(a – b)]

= 0

Q104. The like terms of the following are:

1. 2x , 9x

2. y , xy

3. xy, 9a

4. y , 9x

Ans: 1. 2x , 9x

Q105. (x – y)(x + y) + (y – z)(y + z) + (z – x)(z + x) is equal to:

1. 0

2. x + y + z

3. xy + yz + zx

4. x + y + z

Ans: 1. 0

Solution:

(x – y)(x + y) + (y – z)(y + z) + (z – x)(z + x) = x – y + y – z + z – x = 0

Q106. The factorised form of 3x – 24 is:

1. 3x × 24

2. 3(x – 8)

3. 24(x – 3)

4. 3(x – 12)

Ans: 2. 3(x – 8)

Solution:

We have,

3x – 24 = 3 × x – 3 × 8 = 3(x – 8)

[taking 3 as common]

Q107. The result of subtraction of 3x from -4x is:

1. -7x

2. 7x

3. x

4. -x

Ans: 1. -7x

Solution:

-4x – 3x = -7x

Q108. The value of (a + b) + (a – b) is:

1. 2a + 2b

2. 2a – 2b

3. 2a + 2b

4. 2a – 2b

Ans: 3. 2a + 2b

Solution:

We have,

(a+ b) + (a – b) = (a + b + 2ab) + (a + b – 2ab)

= (a + a ) + (b + b ) + (2ab – 2ab)

= 2a + 2b

Q109. Multiplication of pq + qr + rp and ‘zero’ is:

1. pq + qr

2. pq + rp

3. pq + qr + nrp

4. 0

Ans: 4. 0

Q110. Tick (✓ ) the correct answer:

If x −

1

x = 6, then x2 +

1

x2 = ?

1. 36

2. 38

3. 32

4. 36

1

36

Ans: 2. 36

Solution:

x −

1

x = 6,

Squaring on both sides

x −

1

x

2 = (6)2

⇒ x2 +

1

x2 − 2 = 36

⇒ x2 +

1

x2 = 36 + 2 = 38

Q111. The coefficient of x y in 7pqrx is:

1. 7pqr

2. pqr

3. -7pqr

4. 7

Ans: 1. 7pqr

Q112. Which of the following is the numerical coefficient of x y ?

1. 0

2. 1

3. x

4. y

Ans: 2. 1

Solution:

So, if is asked that the numerical coefficient of 5x then the answer will be 5.

the numerical coefficient is the number, which is before any constant like x, y, z. etc. and we know if we multiply any number or

variable with 1 it remains same.

Here there is no number before (x y ) so we assume it as 1.

Hence the answer is 1.

Q113. Like term as 4m n is:

1. 4m n

2. -6m n

3. 6pm n

4. 4m n

Ans: 2. -6m n

Solution:

We knoe that, the like terms contain the same literal factor. so, the like as 4m n , -6m n , as it contains the same literal factor m n .

Q114. The number of like terms in

1

4 a2bc, −

2

3 bca2,

2

5 ba2c −

1

2 cba2 is:

1. 4

2. 3

3. 6

4. 2

Ans: 1. 4

Solution:

All are like terms.

Q115. The coefficient of xy 2z in -7x 2y 3z is:

1. 7xy

2. 7xy

3. -xy

4. xy

Ans: 1. 7xy

Solution:

-7x y z = (-7xy)(xy z)

Q116. The value of (x + 3) – (x – 3) is:

1. 1 – x

2. 18x + 54

3. 3x – 5

4. 0

Ans: 2. 18x + 54

Q117. The value of (a + b) – (a – b) is:

1. 4ab

2. -4ab

3. 2a + 2b

4. 2a – 2b

Ans: 1. 4ab

Solution:

We have,

(a + b) – (a – b) = a + b + 2ab – (a + b – 2ab)

= a + b + 2ab – a − b + 2ab = a – a + b – b + 2ab + 2ab

= 2ab + 2ab

= 4ab

Q118. Add 9x + 2xy – 3x and 3yx + 2xy – y.

1. 5xy.+x

2. 5yx – x

3. 9x + 5xy – x – y

4. 9x + 5xy + x – y

Ans: 3. 9x + 5xy – x – y

Solution:

9×2 + 2xy − 3x + 3xy + 2x − y

¯

9×2 + 5xy − x − y

Q119. The area of a rectangle whose length and breadth are 9y and 4y respectively is:

1. 4y

2. 9y

3. 36y

4. 13y

Ans: 3. 36y

Solution:

Area = (9y)(4y ) = 36y

Q120. The area of a rectangle whose length and breadth are 3y and 9y respectively is:

1. 21y

2. 27y

3. 12y

4. y

Ans: 2. 27y

Solution:

Area of rectangle = length x breadth = 3y × 9y = 27y

Q121. Tick (✓ ) the correct answer:

(82) – (18) = ?

1. 8218

2. 6418

3. 6400

4. 7204

Ans: 3. 6400

Solution:

(82) – (18)

= (82 + 18)(82 – 18)

= 100 × 64

= 6400

Q122. The number of like terms in 9x , 16x y, – 8x , 12xy , 6x is:

1. 3

2. 2

3. 4

4. 5

Ans: 1. 3

Solution:

9x , – 8x , 6x

Q123. The value of the product 3 +

5

x 9 −

15

x +

25

x2 at x = 1 is:

1. 152

2. 150

3. 148

4. None

Ans: 1. 152

Q124. On dividing p(4p – 16) by 4p(p – 2), we get

1. 2p + 4

2. 2p – 4

3. p + 2

4. p – 2

Ans: 3. p + 2

Solution:

We have,

p ( 4p2 − 16 )

4p ( p − 2 ) =

p [ ( 2p )2 − 42 ]

4p ( p − 2 )

=

( 2p − 4 ) ( 2p + 4 )

4 ( p − 2 )

=

2 ( p − 2 ) .2 ( p + 2 )

4 ( p − 2 )

=

4 ( p − 2 ) ( p + 2 )

4 ( p − 2 )

= p + 2

Q125. The coefficient of x y in -15 x y is:

1. 15

2. -15

3. 3

4. 5

Ans: 2. -15

Q126. The value of 25x + 16y + 40xy at x = 1 and y = -1 is:

1. -48

2. 1

3. 81

4. None

Ans: 2. 1

Q127. Square of 3x – 4y is:

1. 9x – 16y

2. 6x – 8y

3. 9x + 16y + 24xy

4. 9x + 16y – 24xy

Ans: 4. 9x + 16y – 24xy

Solution:

Square of (3x – 4y) will be (3x – 4y)

comparing (3x – 4y) with (a – b)

We get a = 3x and b = 4y

now, using identity, (a – b) = a – 2ab + b

(3x – 4y) = (3x) – 2.3x.4y + (4y)

= 9x + 16y – 24xy

Q128. The Value of

7.83 × 7.83 − 1.17 × 1.17

6.66 is:

1. 9

2. 6.66

3. 1.176

4. None

Ans: 1. 9

Q129. The value of (2x + 4) ÷ 2 is:

1. 2x + 2

2. x + 2

3. x + 4

4. 2x + 4

Ans: 2. x + 2

Solution:

We have,

(2x + 4) ÷ 2

=

2×2 + 4

2

=

2 ( x2 + 4 )

2

= x2 + 2

Q130. The volume of a rectangle with length, breadth and height as 5x, 3x and 7x respectively is:

1. 105x

2. 105x

3. 105x

4. 105x

Ans: 1. 105x

Solution:

Volume of rectangle = Length × breadth × height

V = 5x × 3x × 7x

V = 105x

V = 105x cubic unit.

Q131. The algebraic expression 3x + 2y + 6 is a:

1. Trinomial

2. Monomial

3. Binomial

4. None of the above

Ans: 1. Trinomial

Solution:

The algebraic expression containing three terms is called a trinomial.

Here, 3x, 2y and 6 are three terms.

Q132. The volume of a cube of side 2a is:

1. 4a

2. 2a

3. 8a

4. 8

Ans: 3. 8a

Solution:

Volume = 2a × 2a × 2a = 8a

Q133. The sum of 5x , – 7x , 8x , 11x and -9x is:

1. 2x

2. 4x

3. 6x

4. 8x

Ans: 4. 8x

Solution:

Sum = {5 + (-7) + 8 + 11 + (-9)} x = 8x

Q134. Tick (✓ ) the correct answer:

If (a – b) = 7 and ab = 9, then (a + b ) = ?

1. 67

2. 31

3. 40

4. 58

Ans: 1. 67

Solution:

a – b = 7

ab = 9

a + b = (a – b) + 2ab

= (7) + 2 × 9

= 49 + 18

= 67

Q135. Simplify 4x(5x + 3x) + 2x and find its value for x = 2

1. 20x + 12x + 2x 211

2. 20x + 20x ; 240

3. 20x + 20x ; 120

4. 20x + 12x + 2x ; 212

Ans: 4. 20x + 12x + 2x ; 212

Solution:

Simplifying the given expression, 4x(5x ) + 4x(3x) + 2x = 20x + 12x + 2x

For x = 2, the value of expression = 20(2) + 12(2) + 2(2) = 20 × 8 + 12 × 4 + 4 = 160 + 48 + 4 = 212

Q136. If < a < 1 then the value of a+

1

a is:

1. Greater than 2

2. Grater than 4

3. Less than 4

4. Less than 2

Ans: 1. Greater than 2

Q137. The algebraic expression 3x + 2y + 6 is:

1. monomial

2. Binomial

3. Trinomial

4. None of the above

Ans: 3. Trinomial

Solution:

The algebraic expression containing three terms is called a trinomial.

Here, 3x, 2y and 6 are three terms.

Q138. How many terms are there in the expression 7x + 5x – 5?

1. 1

2. 2

3. 3

4. 5

Ans: 3. 3

Solution:

7x , 5x, – 5