Question

A cistern be filled by one tap in8 Hours and by another in 4 hours how long will it take to fill the cistern if both the tap are opened together

Answer 1

time taken by one tap to fill a cistern= 8 hrs
time taken by another tap to fill a cistern =4 hrs
work done by tap one in 1 hr=1/8
work done by another tap in 1 hr=1/4

work done by both tap( 1/8 +1/4)
=3/8
time taken by both tap to fill a cistern 2 hrs 40 mins

Answer 2

Given:

A cistern can be filled by one tap in = 8 hours

Solution:

A cistern filled by one tap in 1 hour = 1/8

Another cistern can be filled in = 4 hours

Cistern filled by another tap in 1 hour = 1/4

Total cistern filled in 1 hour = 1/4 + 1/8

= (2+1)/8

= 3/8

Therefore:

∴ Cistern can be filled when both the taps are opened together in = 8/3 hours