**CBSE Class 8 Maths – MCQ and Online Tests – Unit 9 – Algebraic Expressions and Identities**

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**CBSE Class 8 Maths – MCQ and Online Tests – Unit 9 – Algebraic Expressions and Identities**

Question 1.

The number of like terms in

\(\frac{1}{4}\)aВbc, – \(\frac{2}{3}\)bcaВ, \(\frac{2}{5}\) baВc, – \(\frac{1}{2}\)cbaВ is

(a) 4

(b) 3

(c) 2

(d) 6.

## Answer

Answer: (a) 4

Hint:

All are like terms.

Question 2.

The like terms of the following are

(a) x, 3x

(b) x, 2y

(c) 2y, 6xy

(d) 3x, 2y

## Answer

Answer: (a) x, 3x

Question 3.

The like terms of the following are

(a) 2xВ, 9xВ

(b) yВ, xy

(c) xy, 9aВ

(d) yВ, 9xВ

## Answer

Answer: (a) 2xВ, 9xВ

Question 4.

The coefficient of xВy in 7pqrxВ is

(a) 7pqr

(b) pqr

(c) -7pqr

(d) 7

## Answer

Answer: (a) 7pqr

Question 5.

The coefficient of xy in xy is

(a) 1

(b) -1

(c) 2

(d) 3.

## Answer

Answer: (a) 1

Hint:

xy = 1(xy).

Question 6.

The value of 5x when x = 5 is

(a) 5

(b) 10

(c) 25

(d) -5.

## Answer

Answer: (c) 25

Hint:

Value = 5 з 5 = 25.

Question 7.

The value of xВ – 2x + 1 when x = 1 is

(a) 1

(b) 2

(c) -2

(d) 0.

## Answer

Answer: (d) 0

Hint:

Value = (1)В – 2(1) + 1 = 0.

Question 8.

The value of xВ + yВ when x = 1, y = 2 is

(a) 1

(b)2

(c) 4

(d) 5.

## Answer

Answer: (d) 5

Hint:

Value = (1)В + (2)В = 5.

Question 9.

The value of xВ – 2yx + yВ when x = 1, y = 2 is

(a) 1

(b) -1

(c) 2

(d) -2.

## Answer

Answer: (a) 1

Hint:

Value = (1)В – 2(2)(1) + (2)В = 1.

Question 10.

The value of xВ – xy + yВ when x = 0, y = 1 is

(a) 0

(b) -1

(c) 1

(d) none of these.

## Answer

Answer: (c) 1

Hint:

Value = (0)В – (0)(1) + (1)В = 1.

Question 11.

Which of the following is a monomial ?

(a) 4xВ

(b) a + 6

(c) a + 6 + c

(d) a + b + c + d.

## Answer

Answer: (a) 4xВ

Hint:

4xВ contains only one term.

Question 12.

Which of the following is a binomial ?

(a) 3xy

(b) 4l + 5m

(c) 2x + 3y – 5

(d) 4a – 7ab + 3b + 12.

## Answer

Answer: (b) 4l + 5m

Hint:

4l + 5m contains two terms.

Question 13.

Which of the following is a trinomial ?

(?) -7z

(b) zВ – 4yВ

(c) xВy – xyВ + yВ

(d) 12a – 9ab + 5b – 3.

## Answer

Answer: (c) xВy – xyВ + yВ

Hint:

xВy – xyВ + yВ contains three terms.

Question 14.

How many terms are there in the expression 5xyВ ?

(a) 1

(b) 2

(c) 5

(d) 3.

## Answer

Answer: (a) 1

Hint:

Only one term 5xyВ.

Question 15.

How many terms are there in the expression 5 – 3xy ?

(a) 1

(b) 2

(c) 3

(d) 5.

## Answer

Answer: (b) 2

Hint:

5, -3xy.

Question 16.

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

(a) 1

(b) 2

(c) 3

(d) 5.

## Answer

Answer: (c) 3

Hint:

7xВ, 5x, -5.

Question 17.

How many terms are there in the expression 4a – lab + 3b + 12 ?

(a) 1

(b) 2

(c) 3

(d) 4.

## Answer

Answer: (d) 4

Hint:

4a, -7ab, 3b, 12.

Question 18.

How many terms are there in the expression 5xy + 9yz + 3zx + 5x – 4y ?

(a) 1

(b) 3

(c) 4

(d) 5.

## Answer

Answer: (d) 5

Hint:

5xy, 9yz, 3zx, 5x, – 4y.

Question 19.

The coefficient in the term 7xy is

(a) 7

(b) 3

(c) 1

(d) 2.

## Answer

Answer: (a) 7

Hint:

Coefficient = 7.

Question 20.

The coefficient in the term -5x is

(a) 5

(b) -5

(c) 1

(d) 2.

## Answer

Answer: (b) -5

Hint:

Coefficient = -5.

Question 21.

The coefficient in the term 20 is

(a) 1

(b) 2

(c) 10

(d) 20.

## Answer

Answer: (d) 20

Hint:

Coefficient = 20.

Question 22.

The coefficient in the term -20 is

(a) -1

(b) -2

(c) -10

(d) -20.

## Answer

Answer: (d) -20

Hint:

Coefficient = -20.

Question 23.

The like terms of the following are

(a) ab, 9ba

(b) ab, -5b

(c) -5b, 9ba

(d) ab, -3a

## Answer

Answer: (a) ab, 9ba

Question 24.

The expression x + 3 is in

(a) one variable

(b) two variables

(c) no variable

(d) none of these.

## Answer

Answer: (a) one variable

Hint:

The only variable is x.

Question 25.

The expression 4xy + 7 is in

(a) one variable

(b) two variables

(c) no variable

(d) none of these.

## Answer

Answer: (b) two variables

Hint:

There are two variables x and y.

Question 26.

The expression x + y + z is in

(a) one variable

(b) no variable

(c) three variables

(d) two variables.

## Answer

Answer: (c) three variables

Hint:

There are three variables x, y and z.

Question 27.

The coefficient of xВy in -15 xВy is

(a) 15

(b) -15

(c) 3

(d) 5.

## Answer

Answer: (b) -15

Question 28.

The product of 4x and 0 is:

(a) 4x

(b) 4

(c) 0

(d) None of the above

## Answer

Answer: (c) 0

Hint:

Anything multiplied by zero is zero.

Question 29.

The volume of a rectangle with length, breadth and height as 5x, 3x^{2} and 7x^{4} respectively is:

(a) 105x^{7}

(b) 105x^{2}

(c) 105x^{4}

(d) 105x

## Answer

Answer: (a) 105x^{7}

Hint:

Volume of rectangle = Length з breadth з height

V = 5x з 3x^{2} з 7x^{4}

V = 105 x^{1+2+4}

V = 105x^{7} cubic unit.

Question 30.

In which of the following, the two expressions are like terms ?

(a) 7x and 7y

(b) 7x and 9x

(c) 7x and 7x^{2}

(d) 7x and 7xy

## Answer

Answer: (b) 7x and 9x

Question 31.

If we subtract 4a – 7ab + 3b + 12 from 12a – 9ab + 5b – 3, then the answer is:

(a) 8a + 2ab + 2b + 15

(b) 8a + 2ab + 2b – 15

(c) 8a – 2ab + 2b – 15

(d) 8a – 2ab – 2b – 15

## Answer

Answer: (c) 8a – 2ab + 2b – 15

Hint:

(12a – 9ab + 5b – 3) – (4a – 7ab + 3b + 12)

= 12a – 9ab + 5b – 3 – 4a + 7ab – 3b – 12

= (12 – 4)a – (9 – 7)ab + (5 – 3)b – 3 – 12

= 8a – 2ab + 2b – 15

Question 32.

If we multiply 5x and (-4xyz), then we get:

(a) 20x^{2}yz

(b) -20x^{2}yz

(c) x^{2}yz

(d) -2xyz

## Answer

Answer: (b) -20x^{2}yz

Hint:

(5x) x (-4xyz)

= 5 з x з (-4) з x з y з z

= -20x^{1+1}yz

= -20x^{2}yz

Question 33.

The coefficient of xy in 6xВyВ is

(a) xy

(b) 2xy

(c) 3xy

(d) 6xy

## Answer

Answer: (d) 6xy

Hint:

6xВyВ = (6xy)(xy).

Question 34.

The coefficient of xy2z in -7x2y3z is

(a) -7xy

(b) 7xy

(c) -xy

(d) xy.

## Answer

Answer: (a) -7xy

Hint:

-7xВyГz = (-7xy)(xyВz).

Question 35.

The sum of 7x, 10x and 12x is

(a) 17x

(b) 22x

(c) 19x

(d) 29x.

## Answer

Answer: (d) 29x.

Hint:

Sum = (7 + 10 + 12) x = 29x.

Question 36.

The sum of 8pq and -17 pq is

(a) pq

(b) 9pq

(c) -9pq

(d) -pq.

## Answer

Answer: (c) -9pq

Hint:

Sum = {8 + (-17)} pq = -9pq.

Question 37.

The sum of 5xВ, -7xВ, 8xВ, 11xВ and -9xВ is

(a) 2xВ

(b) 4xВ

(c) 6xВ

(d) 8xВ.

## Answer

Answer: (d) 8xВ

Hint:

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

Question 38.

The sum of xВ – yВ, yВ – zВ and zВ – xВ is

(a) 0

(b) 3xВ

(c) 3yВ

(d) 3zВ.

## Answer

Answer: (a) 0

Hint:

Sum = (xВ – yВ) + (yВ – zВ) + (zВ – xВ) = 0.

Question 39.

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

(a) 3xy

(b) 5xy

(c) 8xy

(d) xy.

## Answer

Answer: (c) 8xy

Hint:

5xy – (-3xy) = 5xy + 3xy = 8xy

Question 40.

The result of subtraction of 7x from 0 is

(a) 0

(b) 7x

(c) -7x

(d) x.

## Answer

Answer: (c) -7x

Hint:

0 – 7x = -7x.

Question 41.

The result of subtraction of 3x from -4x is

(a) -7x

(b) 7x

(c) x

(d) -x.

## Answer

Answer: (a) -7x

Hint:

-4x -3x = -7x.

Question 42.

The product of 4mn and 0 is

(a) 0

(b) 1

(c) mn

(d) 4 mn.

## Answer

Answer: (a) 0

Hint:

(4 mn)(0) = 0.

Question 43.

The product of 5x and 2y is

(a) xy

(b) 2xy

(c) 5ay

(d) 10ay.

## Answer

Answer: (d) 10ay

Hint:

(5x)(2y) = 10xy.

Question 44.

The product of 7x and -12x is

(a) 84xВ

(b) -84xВ

(c) xВ

(d) -xВ.

## Answer

Answer: (b) -84xВ

Hint:

(7x) (-12x) = – 84xВ.

Question 45.

The area of a rectangle whose length and breadth are 9y and 4yВ respectively is

(a) 4yГ

(b) 9yГ

(c) 36yГ

(d) 13yГ

## Answer

Answer: (c) 36yГ

Hint:

Area = (9y)(4yВ) = 36yГ.

Question 46.

The area of a rectangle with length 2lВm and breadth 3lmВ is

(a) 6lГmГ

(b) lГmГ

(c) 2lГmГ

(d) 4lГmГ.

## Answer

Answer: (a) 6lГmГ

Hint:

Area = (2lВm)(3lmВ) = 6lГmГ.

Question 47.

The volume of a cube of side 2a is

(a) 4aВ

(b) 2a

(c) 8aГ

(d) 8.

## Answer

Answer: (c) 8aГ

Hint:

Volume = 2a з 2a з 2a = 8aГ.

Question 48.

The volume of a cuboid of dimensions a, b, c is

(a) abc

(b) aВbВcВ

(c) aГbГcГ

(d) none of these.

## Answer

Answer: (a) abc

Hint:

Volume = a з b з c = abc.

Question 49.

The product of xВ, – xГ, – x^{4} is

(a) x^{9}

(b) x^{5}

(c) x^{7}

(d) x^{6}

## Answer

Answer: (a) x^{9}

Hint:

Product = (xВ) (-xГ)(-x^{4}) = x^{9}.

Question 50.

(x – y)(x + y) + (y – z)(y + z) + (z – x) (z + x) is equal to

(a) 0

(b) xВ + yВ + zВ

(c) xy + yz + zx

(d) x + y + z.

## Answer

Answer: (a) 0

Hint:

(x – y)(x + y) + (y – z)(y + z) + (z – x) (z + x) = xВ – yВ + yВ – zВ + zВ – xВ = 0.

Question 51.

(a + b)В is equal to

(a) aВ + bВ – 2ab

(b) aВ + bВ + 2ab

(c) aВ + bВ

(d) 2ab.

## Answer

Answer: (b) aВ + bВ + 2ab

Hint:

(a + b)В = aВ + bВ + 2 ab.

Question 52.

(a – b)В is equal to

(a) aВ + bВ – 2ab

(b) aВ + bВ + 2ab

(c) aВ + bВ

(d) 2ab.

## Answer

Answer: (a) aВ + bВ – 2ab

Hint:

(a – b)В = aВ + bВ – 2ab.

Question 53.

aВ – bВ is equal to

(a) 2ab

(b) -2ab

(c) (a + b) (a – b)

(d) ab

## Answer

Answer: (c) (a + b) (a – b)

Hint:

aВ – bВ = (a + b) (a – b).

Question 54.

An algebraic expression that contains only one term is called:

(a) Monomial

(b) Binomial

(c) Trinomial

(d) None of the above

## Answer

Answer: (a) Monomial

Hint:

2x is a monomial

Question 55.

5x + 6y is a:

(a) A. Monomial

(b) Binomial

(c) Trinomial

(d) None of the above

## Answer

Answer: (b) Binomial

Hint:

The expression containing two terms is called binomial.

Question 56.

The algebraic expression 3x + 2y + 6 is

(a) monomial

(b) Binomial

(c) Trinomial

(d) None of the above

## Answer

Answer: (c) Trinomial

Hint:

The algebraic expression containing three terms is called a trinomial. Here, 3x, 2y and 6 are three terms.

Question 57.

A polynomial contains _______ number of terms:

(a) One

(b) Two

(c) Three

(d) Any

## Answer

Answer: (d) Any

Hint:

A polynomial can contain any number of terms, one or more than one.

Question 58.

If we add, 7xy + 5yz – 3zx, 4yz + 9zx – 4y and -3xz + 5x – 2xy, then the answer is:

(a) 5xy + 9yz + 3zx + 5x – 4y

(b) 5xy – 9yz + 3zx – 5x – 4y

(c) 5xy + 10yz + 3zx + 15x – 4y

(d) 5xy + 10yz + 3zx + 5x – 6y

## Answer

Answer: (a) 5xy + 9yz + 3zx + 5x – 4y

Hint:

Given, 7xy + 5yz – 3zx, 4yz + 9zx – 4y and -3xz + 5x – 2xy.

If we add the three expressions, then we need to combine the like terms together.

(7xy – 2xy)+(5yz + 4yz) – 3zx + 9zx – 3xz – 4y + 5x

5y + 9yz + 3zx + 5x – 4y

Question 59.

The number of like terms in 9xГ, 16xВy, -8xГ, 12xyВ, 6xГ is

(a) 3

(b) 2

(c) 4

(d) 5.

## Answer

Answer: (a) 3

Hint:

9xГ, -8xГ, 6xГ.

Question 60.

The number of like terms in

abc, -abc, -bca, acb, bac, \(\frac{1}{2}\)cab is

(a) 6

(b) 4

(c) 3

(d) 2.

## Answer

Answer: (a) 6

Hint:

All are like terms.

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