AP ICET 2017 Shift 2 Paper

Question : 96 of 200

Marks: +1, -0

A tank has three pipes P. Q and R. The pipes P and Q fill it independently in 4 hours and 5 hours respectively while R empties it in 2 hours. If P. Q and R are respectively opened at 1 AM. 2 AM and 3 AM in that order, then the time when the tank will be empty is

4 PM
5 PM
6 PM
7 PM

Validate

Solution:

Part of tank filled at 3 AM just before pipe R is opened

=2/4+1/5=1/2+1/5=7/10

Net part of tank emptied in 1 hour when all the three pipes are open

=1/4+1/5-1/2={5+4-10}/20=-1/20

∴ Time taken to empty

7/10

part of the tank

=(7/10)/(1/20)=14

hours
3 AM + 14 hours = 5 PM.

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