**CBSE Class 8 Maths – MCQ and Online Tests – Unit 7 – Cubes and Cube Roots**

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**CBSE Class 8 Maths – MCQ and Online Tests – Unit 7 – Cubes and Cube Roots**

Question 1.

What is the one’s digit in the cube root of the cube number 5832 ?

(a) 2

(b) 4

(c) 6

(d) 8.

## Answer

Answer: (d)

Hint:

8 × 8 × 8 = 512.

Question 2.

Find the smallest number by which the number 121 must be multiplied to obtain a perfect cube.

(a) 7

(b) 9

(c) 11

(d) 5.

## Answer

Answer: (c)

Hint:

121 = 11 × 11.

Question 3.

Find the smallest number by which the number 88 must be divided to obtain a perfect cube.

(a) 11

(b) 5

(c) 7

(d) 9.

## Answer

Answer: (a)

Hint:

88 = 2 × 2 × 2 × 11 = 2³ × 11.

Question 4.

What is the one’s digit in the cube root of the cube number 6859 ?

(a) 7

(b) 8

(c) 9

(d) 6.

## Answer

Answer: (c)

Hint:

9 × 9 × 9 = 729.

Question 5.

Which of the following numbers is not a cube number ?

(a) 10000

(b) 3125

(c) 64

(d) 729.

## Answer

Answer: (a)

Hint:

10000 = 2 × 2 × 2 × 2 × 5 × 5 × 5 × 5.

= 2^{4} × 5^{4} = 2³ × 2 × 5³ × 5.

Question 6.

The cube of an odd natural number is

(a) even

(b) odd

(c) may be even, may be odd

(d) prime number.

## Answer

Answer: (b)

Hint:

3 × 3 × 3 = 27 (odd).

Question 7.

The cube of an even natural number is

(a) even

(b) odd

(c) may be even, may be odd

(d) prime number.

## Answer

Answer: (a)

Hint:

6 × 6 × 6 = 216 (even).

Question 8.

The one’s digit of the cube of the number 111 is

(a) 1

(b) 2

(c) 3

(d) 9.

## Answer

Answer: (a)

Hint:

1 × 1 × 1 = 1.

Question 9.

The one’s digit of the cube of the number 242 is

(a) 2

(b) 4

(c) 6

(d) 8.

## Answer

Answer: (d)

Hint:

2 × 2 × 2 = 8.

Question 10.

The one’s digit of the cube of the number 123 is

(a) 3

(b) 6

(c) 9

(d) 7.

## Answer

Answer: (d)

Hint:

3 × 3 × 3 = 27.

Question 11.

The one’s digit of the cube of the number 144 is

(a) 1

(b) 2

(c) 3

(d) 4.

## Answer

Answer: (d)

Hint:

4 × 4 × 4 = 64.

Question 12.

The one’s digit of the cube of the number 50 is

(a) 1

(b) 0

(c) 5

(d) 4.

## Answer

Answer: (b)

Hint:

0 × 0 × 0 = 0.

Question 13.

The one’s digit of the cube of the number 326 is

(a) 2

(b) 3

(c) 6

(d) 4.

## Answer

Answer: (c)

Hint:

6 × 6 × 6 = 216.

Question 14.

The one’s digit of the cube of the number 325 is

(a) 2

(b) 5

(c) 3

(d) 6.

## Answer

Answer: (b)

Hint:

5 × 5 × 5 = 125.

Question 15.

The one’s digit of the cube of the number 347 is

(a) 3

(b) 4

(c) 7

(d) 1.

## Answer

Answer: (a)

Hint:

7 × 7 × 7 = 343.

Question 16.

The one’s digit of the cube of the number 68 is

(a) 1

(b) 2

(c) 6

(d) 8.

## Answer

Answer: (b)

Hint:

8 × 8 × 8 = 512.

Question 17.

The one’s digit of the cube of the number 249 is

(a) 2

(b) 4

(c) 9

(d) 1.

## Answer

Answer: (c)

Hint:

9 × 9 × 9 = 729.

Question 18.

What is the one’s digit in the cube root of the cube number 1331 ?

(a) 1

(b) 2

(c) 3

(d) 4

## Answer

Answer: (a)

Hint:

1 × 1 × 1 = 1.

Question 19.

What is the one’s digit in the cube root of the cube number 1000000 ?

(a) 0

(b) 1

(c) 2

(d) 9.

## Answer

Answer: (a)

Hint:

0 × 0 × 0 = 0.

Question 20.

What is the one’s digit in the cube root of the cube number 3375 ?

(a) 2

(b) 3

(c) 5

(d) 4.

## Answer

Answer: (c)

Hint:

5 × 5 × 5 = 125.

Question 21.

What is the one’s digit in the cube root of the cube number 4096 ?

(a) 2

(b) 6

(c) 4

(d) 9.

## Answer

Answer: (b)

Hint:

6 × 6 × 6 = 216.

Question 22.

What is the one’s digit in the cube root of the cube number 4913 ?

(a) 7

(b) 9

(c) 3

(d) 6.

## Answer

Answer: (a)

Hint:

7 × 7 × 7 = 343.

Question 23.

Which of the following numbers is a perfect cube ?

(a) 125

(b) 36

(c) 75

(d) 100.

## Answer

Answer: (a)

Hint:

125 = 5 × 5 × 5 = 5³.

Question 24.

Which of the following numbers is a cube number ?

(a) 1000

(b) 400

(c) 100

(d) 600.

## Answer

Answer: (a)

Hint:

1000 = 10 × 10 × 10 = 10³.

Question 25.

Which of the following numbers is not a perfect cube ?

(a) 1331

(b) 512

(c) 343

(d) 100.

## Answer

Answer: (d)

Hint:

100 = 2 × 2 × 5 × 5 = 2² × 5².

Question 26.

The volume of a cube is 64 cm³. The edge of the cube is

(a) 4 cm

(b) 8 cm

(c) 16 cm

(d) 6 cm.

## Answer

Answer: (a)

Hint:

Edge = \(\sqrt[3]{64}\) = \(\sqrt[3]{2 × 2 × 2 × 2 × 2 × 2}\)

= \(\sqrt[3]{2^3×2^3}\) = 2 × 2 = 4.

Question 27.

Apala makes a cuboid of plasticine of sides 5 cm, 4 cm, 2 cm. How many such cuboids will be needed to form a cube ?

(a) 20

(b) 25

(c) 10

(d) 16.

## Answer

Answer: (b)

Hint:

Volume = 5 × 4 × 2 = 5 × 2 × 2 × 2

= 5 × 2³.

Question 28.

Which of the following is false ?

(a) Cube of any odd number is odd

(b) A perfect cube does not end with two zeroes

(c) The cube of a single digit number may be a single digit number

(d) There is no perfect cube which ends with 8.

## Answer

Answer: (d)

Hint:

1728 = 12³.

Question 29.

What is the one’s digit in the cube root of the cube number 8000 ?

(a) 0

(b) 2

(c) 4

(d) 8.

## Answer

Answer: (a)

Hint:

0 × 0 × 0 = 0.

Question 30.

The number of zeroes at the end of the cube of the number 20 is

(a) 1

(b) 2

(c) 3

(d) 6.

## Answer

Answer: (c)

Hint:

? Number of zeroes at the end of the number 20 = 1

? Number of zeroes at the end of its cube = 3 × 1 = 3.

Question 31.

The number of zeroes at the end of the cube root of the cube number 1000 is

(a) 1

(b) 2

(c) 3

(d) 4.

## Answer

Answer: (a)

Hint:

? Number of zeroes at the end of the cube = 3

? Number of zeroes at the end of the cube root = \(\frac{3}{3}\) = 1.

Question 32.

The number of zeroes at the end of the cube of the number 100 is

(a) 1

(b) 2

(c) 4

(d) 6.

## Answer

Answer: (d)

Hint:

? Number of zeroes at the end of the number 100 = 2

? Number of zeroes at the end of its cube = 3 × 2 = 6.

Question 33.

The number of zeroes at the end of the cube root of the cube number 8000000 is

(a) 1

(b) 2

(c) 3

(d) 6.

## Answer

Answer: (b)

Hint:

? Number of zeroes at the end of the cube = 6

? Number of zeroes at the end of the cube root = \(\frac{6}{3}\) = 2.

Question 34.

Find the smallest number by which the number 108 must be multiplied to obtain a perfect cube.

(a) 2

(b) 3

(c) 4

(d) 5.

## Answer

Answer: (a)

Hint:

108 = 2 × 2 × 3 × 3 × 3 = 2 × 2 × 3³.

Question 35.

Find the smallest number by which the number 250 must be divided to obtain a perfect cube.

(o) 2

(b) 3

(c) 4

(d) 5.

## Answer

Answer: (a)

Hint:

250 = 5 × 5 × 5 × 2 = 5³ × 2.

Question 36.

Find the smallest number by which the number 72 must be multiplied to obtain a perfect cube.

(a) 2

(b) 3

(c) 4

(d) 6.

## Answer

Answer: (b)

Hint:

72 = 2 × 2 × 2 × 3 × 3 = 2³ × 3 × 3.

Question 37.

Find the smallest number by which the number 375 must be divided to obtain a perfect cube.

(a) 2

(b) 3

(c) 5

(d) 4.

## Answer

Answer: (b)

Hint:

375 = 3 × 5 × 5 × 5 = 3 × 5³.

Question 38.

Find the smallest number by which the number 100 must be multiplied to obtain a perfect cube.

(a) 5

(b) 2

(c) 4

(d) 10.

## Answer

Answer: (d)

Hint:

100 = 2 × 2 × 5 × 5.

Question 39.

Find the smallest number by which the number 10000 must be divided to obtain a perfect cube.

(a) 2

(b) 5

(c) 10

(d) 100

## Answer

Answer: (c)

Hint:

10000 = 2 × 2 × 2 × 2 × 5 × 5 × 5 × 5

= 2³ × 2 × 5³ × 5.

Question 40.

Find the smallest number by which the number 200 must be multiplied to obtain a perfect cube.

(a) 2

(b) 10

(c) 5

(d) 100.

## Answer

Answer: (c)

Hint:

200 = 2 × 2 × 2 × 5 × 5 = 2³ × 5 × 5.

Question 41.

Find the smallest number by which the number 625 must be divided to obtain a perfect cube.

(a) 3

(b) 5

(c) 25

(d) 125.

## Answer

Answer: (b)

Hint:

625 = 5 × 5 × 5 × 5 = 5³ × 5.

Question 42.

Find the smallest number by which the number 128 must be multiplied to obtain a perfect cube.

(a) 2

(b)4

(c) 3

(d) 8.

## Answer

Answer: (b)

Hint:

128 = 2 × 2 × 2 × 2 × 2 × 2 × 2

= 2³ × 2³ × 2.

Question 43.

Find the smallest number by which the number 256 must be divided to obtain a perfect cube.

(a) 2

(b) 4

(c) 8

(d) 16.

## Answer

Answer: (b)

Hint:

256 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2

= 2³ × 2³ × 2 × 2.

Question 44.

Find the smallest number by which the number 36 must be multiphed to obtain a perfect cube.

(a) 6

(b) 2

(c) 3

(d) 4.

## Answer

Answer: (a)

Hint:

36 = 2 × 2 × 3 × 3.

Question 45.

Find the smallest number by which the number 1296 must be divided to obtain a perfect cube.

(a) 6

(b) 2

(c) 4

(d) 3.

## Answer

Answer: (a)

Hint:

1296 =2 × 2 × 2 × 2 × 3 × 3 × 3 × 3

= 2³ × 2 × 3³ × 3.

Question 46.

Find the smallest number by which the number 392 must be multiplied to obtain a perfect cube.

(a) 3

(b) 5

(c) 7

(d) 6.

## Answer

Answer: (c)

Hint:

392 = 2 × 2 × 2 × 7 × 7 = 2³ × 7 × 7.

Question 47.

Find the smallest number by which the number 2401 must be divided to obtain a perfect cube.

(a) 7

(b) 6

(c) 5

(d) 9.

## Answer

Answer: (a)

Hint:

2401 = 7 × 7 × 7 × 7 = 7³ × 7.

Question 48.

What is the one’s digit in the cube root of the cube number 1728 ?

(a) 1

(b) 2

(c) 3

(d) 9.

## Answer

Answer: (b)

Hint:

2 × 2 × 2 = 8.

Question 49.

What is the one’s digit in the cube root of the cube number 2197 ?

(a) 1

(b) 2

(c) 3

(d) 7.

## Answer

Answer: (c)

Hint:

3 × 3 × 3 = 27.

Question 50.

What is the one’s digit in the cube root of the cube number 2744 ?

(a) 1

(b) 2

(c) 3

(d) 4.

## Answer

Answer: (d)

Hint:

4 × 4 × 4 = 64.

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