Question

Three workers have to do a certain job. The first worker can finish the job in 8 hours. The second worker can finish the job in 4 hours. The third worker can also finish the job in 4 hours. How long will it take the three workers to finish the job if they work together?

PLS help

Answer 1

Working together three workers would take 1 hour 36 minutes to finish the job

Solution:

Given that first worker can finish the job in 8 hours

So in one hour, first worker can do
`(1)/(8)` th of the work

The second worker can finish the job in 4 hours

So in one hour, second worker can do
`(1)/(4)` th of the work

The third worker can also finish the job in 4 hours

So in one hour, third worker can do
`(1)/(4)` th of the work

The three workers working together in 1 hour can do:

`(1)/(8) + (1)/(4) + (1)/(4) = (1 + 2 + 2)/(8) = (5)/(8)`

The three worker can thus do
`(5)/(8)` th of the work in one hour

Hence the three of them together can finish the work in
`(8)/(5)` hours

`(8)/(5) = 1(3)/(5)` hours

Thus working together three workers would take 1 hour 36 minutes to finish the job