1.

Two pipes A and B can fill a tank in 15 hours and 20 hours respectively while a third pipe C can empty the full tank in 25 hours. All the three pipes are opened in the beginning. After 10 hours, C is closed. The time taken to fill the tank is ?

A. 12 hours
B. 13
C. /
D. 16 hours
E. 18 hours
Answer» B. 13


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