MCQs Questions on Class 8 Algebraic Expressions and Identities
1. An algebraic expression that contains only one term is called:
A. Monomial
B. Binomial
C. Trinomial
D. None of the above
Answer: A
Example: 2x is a monomial
2. 5x+6y is a:
A. Monomial
B. Binomial
C. Trinomial
D. None of the above
Answer: B
Explanation: The expression containing two terms is called binomial.
3. The algebraic expression 3x+2y+6 is a:
A. Monomial
B. Binomial
C. Trinomial
D. None of the above
Answer: C
Explanation: The algebraic expression containing three terms is called a trinomial. Here, 3x, 2y and 6 are three terms.
4. A polynomial contains _______ number of terms:
A. One
B. Two
C. Three
D. Any
Answer: D
Explanation: A polynomial can contain any number of terms, i.e. one or more than one.
5. In which of the following, the two expressions are like terms?
A. 7x and 7y
B. 7x and 9x
C. 7x and 7x2
D. 7x and 7xy
Answer: B
6. 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: A
Explanation: 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
= 5xy + 9yz + 3zx + 5x – 4y
7. 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: C
Explanation: (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
8. If we multiply 5x and (– 4xyz), then we get:
A. 20x2yz
B. -20x2yz
C. x2yz
D. -2xyz
Answer: B
Explanation: (5x) x (-4xyz)
= 5 × x × (-4) × x × y × z
= -20x1+1yz
= -20x2yz
9. The product of 4x and 0 is:
A. 4x
B. 4
C. 0
D. None of the above
Answer: C
Explanation: Any value multiplied by zero is zero.
10. The volume of a cuboid with length, breadth and height as 5x, 3x2 and 7x4 respectively is:
A. 105x7
B. 105x2
C. 105x4
D. 105x
Answer: A
Explanation: Volume of cuboid = Length × breadth × height
V = 5x × 3x2 × 7x4
V = 105 x1+2+4
V = 105x7 cubic units
11. The product of 5x and 3y is:
A. xy
B. 2xy
C. 5xy
D. 15xy
Answer: (D) 15xy
(5x)(3y) = 15xy
12. The product of 6x and -11x is:
A. 66x²
B. -66x²
C. x²
D. -x²
Answer: B. -66x²
(6x) (-11x) = –66x²
13. The area of a rectangle whose length and breadth are 3y and 9y² respectively is:
A. 12y³
B. 21y³
C. 27y³
D. y³
Answer: C. 27y³
Explanation:
Area of rectangle = length x breadth = 3y x 9y² = 27y³.
14. The area of a rectangle that has length = 2a²b and breadth = 3ab² is:
A. 6a³b³
B. a³b³
C. 2a³b³
D. 4a³b³
Answer: A. 6a³b³
Explanation:
Area of rectangle = (2a²b)(3ab²) = 6a³b³
15. The side of a cube is 2a. Find the volume of the cube.
A. 4a²
B. 2a
C. 8a³
D. 8
Answer: C. 8a³
Explanation:
Volume of the cube = 2a × 2a × 2a = 8a³
16. Multiplication of monomials x², (–x)³, (–x)4 is equal to:
A. x9
B. x5
C. x7
D. x6
Answer: A. x9
Explanation:
(x²).(-x³).(-x)4 = x9
17. The value of (x – y)(x + y) + (y – z)(y + z) + (z – x) (z + x) is:
A. x + y + z
B. x² + y² + z²
C. xy + yz + zx
D. 0
Answer: D. 0
Explanation:
(x – y)(x + y) + (y – z)(y + z) + (z – x) (z + x)
= x² – y² + y² – z² + z² – x² [By algebraic identity: a2 – b2 = (a+b) (a-b)]
= 0
18. (a – b)² is equal to:
A. a² + b² – 2ab
B. a² + b² + 2ab
C. a² + b²
D. 2ab
Answer: A. a² + b² – 2ab
Explanation: By algebraic identity,
(a + b)² = a² + b² – 2 ab
19. The product of 3xy2z and 4x is:
A. 12xyz
B. 12xy2
C. 12x2y2z
D. 12x2yz
Answer: C. 12x2y2z
Explanation: The product of 3xy2z and 4x is:
⇒ (3xy2z) (4x)
⇒ 3.x.y2.z.4.x
⇒ 12x2y2z
20. Which of the following is a like term as 8xy?
A. 8
B. 8x
C. 8y
D. xy
Answer: D. xy
ANSWERS :- 28. III