Question

The temperature of a metal coin is increased by ${100}^o$C and its diameter increases by $0.15$%. Its area increases by nearly :

• A. $0.15$%
• B. $0.60$%
• C. $0.30$%
• D. $0.0225$%

Answer 1

The correct option is C $0.30$%

$A=\frac{1}{4}\pi d^2$ where $d$ is diameter of coin.

When diameter increased by $0.15$% then the area will be doubled of increase in diameter.

Increase in area $=2\times 0.15$%

$=0.30$%