Question

If the rate of burning is $2$ cm${}^3$ $/3$ min, how long will this candle burn?

• A. $2$ hours
• B. $1$ hour
• C. $1.5$ hours

Answer 1

The correct option is A $2$ hours

Length of the candle $l=4$ cm
Breadth of the candle $b=2$ cm
Height of the candle $h=10$ cm
$\therefore$ Volume of the candle $=10\times 4\times 2=80$ cm${}^3$

$\text{Time taken in burning}2c{m}^3=3minutes$
$\text{Time taken in burning}1c{m}^3=\frac{3}{2}minutes$
$\therefore \text{Time taken in burning}80c{m}^3=\frac{3}{2}\times 80minutes$
$=\frac{240}{2}=120minutes$
$=2hours$ .

Option (a.) is correct.