Question

Tap A can fill a cistern in 5 hours. Tap B can fill the cistern in 4 hours. Both the taps are opened together. After two hours, tap B is closed. How long will tap A take to fill the remaining cistern?​

Answer 1

Answer:

30 minutes

Step-by-step explanation:

Cistern filled in 1 hour by Tap A = 1/5

Cistern filled in 1 hour by Tap B = 1/4

Cistern filled by both taps in 1 hour = 1/5 + 1/4 = 9/20

Cistern filled by both taps in 2 hours = 9/10

Remaining cistern = 1/10

Hence, time taken by Tap A to fill remaining cistern = 1/10 ÷ 1/5 = 1/10 × 5 = 1/2 hours or 30 minutes.