Answer:
The correct option is B) 12.
Step-by-step explanation:
Consider the provided information.
Working alone at its constant rate, pump X pumped out ¼ of the water in a tank in 2 hours.
As we know: ,
The rate of pump X is
of the water is pumped out of the tank, that means only
is left to be pumped out.
All 3 pumps pumped out the remaining of the water out in 3 hours.
The combined rate of all three pumps is:
Pump Y, working alone at its constant rate, would have taken 18 hours to pump out the rest of the water.
The rate of pump Y =
Let z is the time taken by pump Z, then the rate of pump Z is .
Therefore,
Multiplying both sides by 24 z.
Hence, the correct option is B) 12.