Question

• Two taps can fill a tank in 6 hours and 8 hours
respectively. An outlet can empty the tank in
10 hours. Both the taps and the outlet were
opened and allowed to run for 4 hours, after
which the second tap and the outlet were
closed. How long will it take the first tap to fill
the remaining tank?​

Answer 1

From the information, in 1 hour;

Tap A, running alone, would fill 1/10 of the tank.

Tap B, running alone, would fill 1/15 of the tank.

Running together, both taps would fill

1/10+1/15= 1/6 of the tank in 1 hour I.e it would take 6 hours to fill the tank with both taps

running.

If Tap A alone runs for 8 hours it would fill 1/10 x 8 hours = 4/5 of the tank.

This means both taps had already filled 1/5 when they were running together.

Since 1/6 of the tank is filled per hour when both tanks are running, how much time would both take to fill 1/5 of the tank. DIVIDE

=1/5 ÷ 1/6

=1.2 hours =1 hour 12 minutes

Both taps were running for that time before tap B was closed.

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