Question

A tap can fill a tank of 500 litres in 3 hours 30 minutes. In how much time will it fill one fifth of the tank?

Answer 1

One fifth of 500 liters of tank=$\frac{1}{5}\times 500=100l$

Time take to fill 500 liters=3.5 hours

using unitary method,

time take to fill 100 liters=

$\begin{array}{c}\frac{3.5}{500}\times 100=0.7hr\\ =0.7\times 60min\\ =42min\end{array}$

Thus, in 42 minutes tank would be one fifth filled.