Question

Kevin, can clean a stadium in 5 hours working alone. Chris, can

clean the same stadium in 3 hours. How long will it take for both
Kevin and Chris to clean the stadium if they work together?

Answer 1

Answer: It will about 1.88 hours or 1 hour 52.5 minutes to clean the stadium if they work together .

Explanation:

Given : Time taken by Kevin to clean a stadium = 5 hours

Rate of work done by Kelvin =
`(1)/(5)`

Time taken by Chris to clean a stadium = 3 hours

Rate of work done by Chris =
`(1)/(3)`

Let t be the time taken by both of them to clean the stadium together.

According to the question , we have

Rate of work done together = Rate of work done by Kelvin+Rate of work done by Chris

`(1)/(t)=(1)/(5)+(1)/(3)\\\\ \Rightarrow\ (1)/(t)=(3+5)/(15)\\\\ \Rightarrow\ (1)/(t)=(8)/(15)\\\\\Rightarrow\ t=(15)/(8) =1.875`

`t=1+0.875` hours

`t=1\text{ hour }+0.875(60)\text{ minutes}` [∵ 1 hour = 60 minutes]

`t=1\text{ hour }+52.5\text{ minutes}= \text{1 hour 52.5 minutes}`

Hence, It will about 1.88 hours or 1 hour 52.5 minutes to clean the stadium if they work together .