Pipes P and Q can fill a storage tank in full with water in 10 and 6 minutes, respectively. Pipe R draws the water out from the storage tank at a rate of 34 litres per minute. P, Q and R operate at a constant rate. If it takes one hour to completely empty a full storage tank with all the pipes operating simultaneously, what is the capacity of the storage tank (in litres)?
A. 27.5
B. 60.0
C. 120.0
D. 127.5
GATE 2022 · General Aptitude · Work Time · medium
Answer: The capacity of the storage tank is 120 litres.
Combined fill rate of P and Q: P + Q fill rate = 4C/15 litres per minute
Net drain rate: Net outflow = 34 - 4C/15 litres per minute
Set up and solve the equation: 60 * (34 - 4C/15) = C => 2040 - 16C = C => 2040 = 17C => C = 2040/17 = 120