Question

A tank can be filled by one tap in 10 minutes and by another in 30 minutes. Both the taps are kept open for 5 minutes and then the first one is shut off. In how many minutes more is the tank completely filled?

Accepted Answer

C. Tap A fills $\frac{1}{10}$ of tank/min, Tap B fills $\frac{1}{30}$ of tank/min. In 5 minutes together, fraction filled = $5 	imes \left(\frac{1}{10} + \frac{1}{30}ight) = 5 	imes \frac{4}{30} = \frac{20}{30} = \frac{2}{3}$. Remaining fraction = $1 - \frac{2}{3} = \frac{1}{3}$. Time required by Tap B alone to fill remaining fraction = $\frac{1/3}{1/30} = 10$ minutes.

Pipes and Cisterns - Time to Fill Tank

Explanation

Practise this under exam conditions