Question

A cuboidal metal of dimensions $44cm\times 30cm\times 15cm$ was melted and cast into a cylinder of height $28$cm. Its radius is ________.

• A. $20$cm
• B. $15$cm
• C. $10$cm
• D. $25$cm

Answer 1

The correct option is B $15$cm

Volume of the cuboidal metal $=44\times 30\times 15=19800$ cm${}^3$

It is casted into a cylinder, therefore the volume remains unchanged.

Given that, height of cylinder $=28$ cm

$\Rightarrow$ Volume of cylinder $=\pi r^{2}h=19800$

$\Rightarrow r^2=225$ cm${}^2$

$\therefore r=15$ cm