Question

It takes Tony 15 hours to rake the front lawn while his brother, Jose, can rake the lawn in 12 hours. How long will it take them to take the lawn working together?

Answer 1

they can finish

`(1)/(15) + (1)/(12) \\`

in one hour

`(4 + 5)/(60) \\ (9)/(60)`

in 6 hours they can finish

`(9)/(60) * 6 \\ (54)/(60)`

so the left work

`(60 - 54)/(60)`

`(6)/(60)`

they can perform

`(3)/(60) work in60 \: minutes / 3`

so the can perform

`(6)/(60) work \: in \: 20minutes * 2`

the take 6 hours and 40 minutes