Question

What is the minimum number we need to multiply with 392 to make it a perfect cube?

• A. 4
• B. 7
• C. 2
• D. 6

Answer 1

The correct option is B

7

$\begin{array}{cc}2& 392\\ 2& 196\\ 2& 98\\ 7& 49\\ & 7\end{array}$

Prime factor of 392 = 2 × 2 × 2 × 7 × 7

For perfect cube number the factors should be forming the triplet. Here 2 is forming the triplet but 7 does not.

To make it a perfect cube we need to multiply it with 7.

392 × 7 = 2 × 2 × 2 × 7 × 7 × 7 = 2744