a worker has a new pump and an old pump. the new pump can fill a tank in five hours and the old pump can fill the same tank in 7 hours write and solve an equation for the time it will take both pumps to fill one tank if the pumps are used together.

Answer 1

rate of old pump = tank/7
rate of new pump = tank/5
combined rate = tank/7 + tank/5
= (5tank + 7tank)/35 = 12tank/35

combined time = tank/(12tank/35)
= 35/12
= 2 11/12 hours = 2hours and 55 minutes

Answer 2

2 Hours 55minutes