Class 8 Maths – Chapter 7
Cubes & Cube Roots

Important Exam Questions (Solved)

Q1. Find the cube of 7.

Solution:

Cube of a number = number × number × number

7³ = 7 × 7 × 7 = 343

Answer: Cube of 7 = 343

Q2. Find the cube of −5.

Solution:

(−5)³ = −5 × −5 × −5

= −125

Answer: Cube of −5 = −125

Q3. Find the cube root of 125.

Solution:

125 = 5 × 5 × 5

∛125 = 5

Answer: Cube root of 125 = 5

Q4. Find the cube root of 1728.

Solution:

1728 = 12 × 12 × 12

∛1728 = 12

Answer: Cube root of 1728 = 12

Q5. Check whether 216 is a perfect cube.

Solution:

Prime factorisation:

216 = 2 × 2 × 2 × 3 × 3 × 3

Grouping factors in 3s:

(2 × 2 × 2) and (3 × 3 × 3)

∛216 = 2 × 3 = 6

Answer: Yes, 216 is a perfect cube.

Q6. Find the smallest number by which 108 must be multiplied to get a perfect cube.

Solution:

108 = 2 × 2 × 3 × 3 × 3

We need one more 2 × 2 to make groups of 3

Required number = 4

Answer: Required number = 4

Q7. Find the cube root of −512.

Solution:

512 = 8 × 8 × 8

∛(−512) = −8

Answer: Cube root of −512 = −8

Q8. Find the cube root of 13824.

Solution:

13824 = 24 × 24 × 24

∛13824 = 24

Answer: Cube root of 13824 = 24

📌 Exam Tip

• Write prime factorisation neatly
• Group factors clearly in 3s
• Always underline the final answer

✨ Prepared for CBSE Class 8 by Shaktimatha Learning