Four pipes A B C and D can fill a tank with water in 15 20 30 and 60 hours respectively Pipe A is op...........

Quantitative Aptitiude (CLAT) Pipes&cistern

Four pipes A, B, C and D can fill a tank with water in 15, 20, 30 and 60 hours respectively. Pipe A is opened at 4 a.m., B at 5 a.m., C at 6 a.m. and D at 7 a.m. When is the tank filled up completely?

9.30am

10.00am

10.30am

11.00am

Explanation:

4t+3(t-1)+2(t-2)+t-3=60,
4t+3t-3+2t-4+t-3=60,
10t-10=60,
10t=70 hence t=7 hrs ,
The tank will get filled 7 hrs from 4:00 AM,ie 11:00 AM.
Henec, option 4 is the correct answer.