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Tap A can fill a tank in 10hrs,Tap B can fill it in 20hrs, and an out [#permalink]

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22 Nov 2017, 12:28

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Question Stats:

70% (01:53) correct 30% (02:56) wrong based on 73 sessions

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Tap A can fill a tank in 10hrs,Tap B can fill it in 20hrs, and an outlet,Tap C can empty the tank in 30hrs. Each tap is opened,one by one,for exactly one hr and then closed. If its 7AM,the tank is 1/4th full and taps work in alphabetic order(A then B and then C),at what time will the tank begin to overflow?

Tap A can fill a tank in 10hrs,Tap B can fill it in 20hrs, and an out [#permalink]

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22 Nov 2017, 12:47

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Assume capacity of the tank is 600 units.

The rate of filling the taps by Tap A is 60 units/hr, Tap B is 30 units/hr, and Tap C empties the tank at the rate of 20 units/hr

At 7 AM, the tank is 1/4th full, hence we have 150 units of water.

Every 3 hours, the first two taps fill 90 units and in the third hour, the Tap C empties the tank by 20 units. Therefore, in 3 hours, the tank is filled with 70 units of water. So in 18 hours, the tap fills about 420 units of the remaining 450 units. The time is now 1 AM

Now as the Tap A starts filling up the tank, half an hour later, the tank is full and starts overflowing. Therefore, the time when the tank starts overflowing is 1:30 AM next day(Option A) _________________

Tap A can fill a tank in 10hrs,Tap B can fill it in 20hrs, and an outlet,Tap C can empty the tank in 30hrs. Each tap is opened,one by one,for exactly one hr and then closed. If its 7AM,the tank is 1/4th full and taps work in alphabetic order(A then B and then C),at what time will the tank begin to overflow?

Tap A can fill a tank in 10hrs,Tap B can fill it in 20hrs, and an out [#permalink]

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30 Nov 2017, 21:49

Sangeeta2018 wrote:

Tap A can fill a tank in 10hrs,Tap B can fill it in 20hrs, and an outlet,Tap C can empty the tank in 30hrs. Each tap is opened,one by one,for exactly one hr and then closed. If its 7AM,the tank is 1/4th full and taps work in alphabetic order(A then B and then C),at what time will the tank begin to overflow?

in each 3 hour cycle, 1/10+1/20-1/30=7/60 of the tank is filled 3/4, or 45/60, of the tank needs to be filled after 6 cycles, or 18 hours, at 1 AM next day, 6*7/60=42/60 of the tank has been filled, leaving 3/60 to be filled (3/60)/(1/10)=1/2 hour more needed from Tap A 1:30 AM A