Question

John is trying to drain a swimming pool. he has two pumps, but he can only use one at a time. he knows that the time a pump takes to drain the pool varies inversely with the power in watts of the pump. his old pump is a 40 watt pump, and it can drain the pool in 5 hours. how long would the job take if he uses his new 100 watt pump?

Answer 1

The time varies inversely with power is mathematically expressed as
time = k/power (where k = constant of variation)
Provided that a 40-watt old pump which can take to drain the water in 5 hours. So,
5 hrs = k/(40 watts)
k = 200 hrs/watt

Then if he use the new pump, then the time taken would be
time = (200 hrs/watt)/(100 watts)
time = 2 hours