Question

Pipes A can fill a tank in 30 minutes while pipe B can fill it in 45
minutes. An other pipe C can empty a full tank in 60 minutes.
If all three pipes are opened simultaneously, The empty tank
will be filled in
A. `2/7` hour
B. `3/7` hour
C. `4/7` hour
D. `5/7` hour

Answer 1

Correct Answer - (b)
Part of tank filled by all three pipes in 1 minute
`= 1/30 + 1/45 - 1/60=(6+4-3)/180 = 7/180`
Time taken `= 180/7` minutes
`= 180/(7 xx60) = 3/7` hour