Two pipes P and Q can fill a cistern in 18 and 24 minutes respectively. Both pipes are opened, but after some time, the slower pipe is closed. The cistern gets filled in 12 minutes from the start. When is the slower pipe closed?
P fill the cistern = 18 min
Q fill the cistern = 24 min
Total work done = LCM (18,24)= 72
P's efficiency = $$\frac{72}{18}$$ = 4
Q's efficiency = $$\frac{72}{24}$$ = 3
Tank will be fiiled= $$\frac{72}{7}$$hours
Tap P is open for 12 min  and taps Q closed after some time
so
as we know that ,
efficiency multiplied by time = work
$$4\times 12 + 3\times T$$= 72
T = 8 min
Create a FREE account and get:
Day-wise Structured & Planned Preparation Guide
By proceeding you agree to create your account
Free CAT Schedule PDF will be sent to your email address soon !!!
