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Tap A can fill a tank in 40 min and Tap B can empty the tank in 60 min. If the taps are opened at the same time, then the time taken to fill the tank
Question

Tap A can fill a tank in 40 min and Tap B can empty the tank in 60 min. If the taps are opened at the same time, then the time taken to fill the tank will be:

A.

120 min

B.

100 min

C.

125 min

D.

150 min

Correct option is A

Given:
A can fill a tank in 40 min
B can empty the tank in 60 min
Solution:
Convert minutes into efficiency
Take LCM of 40 and 60
LCM (40, 60) = 120
Now, units of time taken by pipe A = 12040\frac{120}{40}​ => Units = 3
Units of time taken by pipe B = 12060\frac{120}{60}​ => Units = 2
Time taken by tank to fill the whole tank when both pipes are open =  ​120(32)\frac{ 120}{(3 - 2)} => T = 120 minutes​

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