Question

A new type of pump can drain a certain pool in 5 hours. An older pump can drain the pool in 15 hours. How long will it take both pumps working together to

drain the pool?
Do not do any rounding.
hours

Answer 1

New pump:

`\text{5 hours = 1 pool}`

`\text{1 hour} = (1)/(5) \ \text{pool}`

Old pump:

`\text{15h = 1 pool}`

`\text{1h} = (1)/(15) \ \text{pool}`

If both work together

`\text{1h} = (1)/(5)+ (1)/(15)= (4)/(15) \ \text{pool}`

`(4)/(15) \ \text{pool = 1 hour}`

`(1)/(15) \ \text{pool} = (1)/(4) \ \text{hour}`

`(15)/(15) \ \text{pool} =(1)/(4) *15`

1 pool = 3.75 hours or 3 hours 45 mins