Question

a swimming pool is filled in 30 hours by two identical pumps. how much quicker would it be filled if five similar pumps were used instead?

Answer 1

30=x/2 where x is time -- multiply by 2
x=60 One pump would take 60h to fill it up.

60/5=12 It would take 12 hours for 5 pumps.

Answer 2

30x2=60 (to find one pump)
60/5=12

It would take 12 hours so it would be quicker by 18 hours