Question

A solid metal ball of radius 8 cm is melted and cast into smaller balls, each of radius 2 cm. The number of such balls is:

• A. 8
• B. 16
• C. 32
• D. 64

Answer 1

The correct option is D 64

Let we cast big ball into $n$ number of small balls.

Therefore,

Volume of big ball =n$\times$ Volume of small balls

$⟹\frac{4}{3}\pi (8{)}^3=n(\frac{4}{3}\pi \left(2{)}^3\right)$

$⟹n=\frac{512}{8}=64$

Hence the number of such balls is $64$.