Question 7

A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken for the tank to get filled?

Solution

Time to fill tank with 1 tap = 6hrs

Therefore, time to fill half tank = 6/2 = 3hrs.

4 taps fill remaining half.

Efficiency per tap = 1/6

Let the time taken for remaining half tank be t.

Efficiency x time = work

$$ (\frac{1}{6} \times 4)t = 0.5 $$

i.e t = 3/4 hrs =$$ \frac{3}{4} \times 60 $$ mins = 45 minutes.

Total time = 3hrs + 45 minutes

Therefore, Option D is correct.

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