Question

Qus 17: A cistern can be filled by one tap in 4 hours and by another in 3 hours. How long will it take to fill if both taps are opened together ?​

Answer 1

Time taken by tap 1 to fill the cistern = 4h

work done in 1h = 1/4

time taken by tap 2 to fill the cistern = 3h

work done in 1 h = 1/3

one hour work of both taps = 1/4+1/3 =7/12

time taken by both taps to fill cistern =1÷7/12

=12/7 h ans