Question

Phil can paint the garage in 12 hours and Rick can o it in 10 hours. If they work together for 3 hours and then Phil leaves, how long will it take rick to finish the job?

Answer 1

It will take 4.5 hours for rick to complete the job.

Explanation:

Given:

Time taken by Phil to paint the garage = 12 hours.

It means that for each hour he does =
`(1)/(12)`of the job.

.

Time taken by Rick to paint the garage = 10 hours.

It means that for each hour he does =
`(1)/(10)` of the job

.

If they work together for 3 hours,

Phil does job in 3 hrs =
`3*(1)/(12) = (1)/(4)=0.25`

Rick does job in 3 hrs =
`3*(1)/(10) = (3)/(10)=0.3`

.

So in three hours of working together job done =
`0.3+0.25 = 0.55`

.

This means job of the painting entire garage have been done 0.55 of it.

1 - 0.55 = 0.45.

So there is 0.45 job left

At this point Phil quits and Rick presses on by himself. Since he does 1/10 of the garage every hour

Let T represents the time that Rick needs to complete the job after Phil leaves.

Hence,
`(1)/(10)* T= 0.45\\\\T = 0.45 * 10\\T =4.5 hrs`

Hence it will take rick 4.5 hours to complete the remaining job.