1.

Two pipes A and B can fill a tank in 15 hours and 20 hours respectively while a therd 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. Now how much time more is required to fill the tank?

Answer»

2 hrs
3 hrs
6 hrs
1 hr

Solution :LET the required time be T hours. Now PART filled by A
in `(10+T)` hours + part filled by B in `(10+T)` hours +
part empty by C in 10 hours = 1
` RARR (T+10)/15 + (T+10)/20 - 10/25 = 1 rArr T = 2 hrs`


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