Question

a swimming pool can be filled in 10 hours by 6 pumps working together how much time will 4 pumps take to fill it up

Answer 1

The number of pumps has an inverse proportion relationship with the number of hours needed to fill up the pool

⇒ the more pumps = the lesser hours needed

6 pumps = 10 hours (given)

Find 1 pump:

1 pump = 10 x 6 = 60 hours

Find 4 pumps:

4 pumps = 60 ÷ 4 = 15 hours

Answer: It will need 15 hours

Answer 2

Time taken by 6 pumps - 10 hours Time taken by 1 pump - (10×6) hours Time taken by 4 pumps - 60÷4 hours = 15 hours