Question

Two pipes A and B can fill a tank in 15
minutes and 20 minutes respectively. Both the
pipes are opened together but after 4 minutes,
pipe A is turned off. What is the total time
required to fill the tank?
(a) 10 min 20 sec (b) 11 min 45 sec
(c) 12 min 30 sec (d) 14 min 40 sec​

Answer 1

Answer:

A in 1 min = 1/15

Bin. 1min = 1/20

A+Bin I min = 1/15 +1/20=

= 4/60 +3/60=7/60

A+B in 4 min = 7x4/6o=28/60

= 7/15.

Remaining=1-7/15=8/15

B will finish=8/15x20/1

160/15=32/3 min = 10 min 40 sec

TOTAL=4min+10min.40 sec

=14 min 40 sec. (d) Ans