Question

Carrie can inspect a case of watches in two hours. Jerry inspects a case in five hours. After inspecting a case for a half an hour, Carrie takes a break. In the mean time, Jerry takes over and completes the job, how long did this take him?

Answer 1

It will take Jerry 3 hr 45 minutes to complete the work.

Explanation:

Let Jerry takes x hours.

Carrie's rate = 1/2 case/hr

Jerry rate's = 1/5 case/h

We know that work done =rate x time

So, Carrie work + Jerry work = 1 job complete

`(1)/(4) +(x)/(5) =1`

`(5+4x)/(20) =1`

`5+4x=20`

`4x =20-5`

`4x=15`

x = 15/4 =
`3(3)/(4)`

= 3 hr 45 minutes

Hence, it will take Jerry 3 hr 45 minutes to complete the work.