Question

How long will it take for two pipes A and B to fill an empty cistern if they worked alternately for an hour each ?
A. Working alone, Pipe A can fill the cistern in 40 hours
B. Pipe B is one third as efficient as Pipe A

A) Only A is sufficient B) Only B is sufficient C) Both (

Answer 1

Statement 1: Working alone, Pipe A can fill the cistern in 40 hours

We do NOT know the rate of Pipe B hence

NOT SUFFICIENT

Statement 2: Pipe B is one third as efficient as Pipe A

B = A/3 but we need to calculate the time and we do NOT have any specifics of time taken by A and B hence

NOT SUFFICIENT

Combining the two statements

A fills in 40 hours i.e .Time of Pipe B = 3*30 = 120 hours

No we can find how much time will they take to fill the tank as we have the exact rates of pipes hence

SUFFICIENT

Answer: Option C