Question

28 pumps can empty a reservoir in 18 hrs. In how many hrs can 42 such pumps can do the same work ?

Answer 1

28 pumps take 18hours.

So,

1 Pump will take
28×18 hours
=504 hours

Hence42 pumps will take 504/42= 12 hours


Answer is 12 hours



Remember that first to find the time required for 1 Pump... We need to multiply because... If work of 28 pump is doing by 1 Pump usually it requires more time, get multiplied...

Similarly second case we divide by 42 because... If 42 pumps are there for doing the 1 Pumps work... It will take lesser time, get divided...

Hope helpful to you...