Question

Rachel can finish the job in 5 hours, while Carl can finish the same job in 8 hours. How long will it take them to finish the job together?

Answer 1

Answer:

3.08 hours

Step-by-step explanation:

Rachel can finish the job in 5 hours.

Part of work done be Rachel in one hour = 1/5

Carl can finish the same job in 8 hours.

Part of work done be Carl in one hour = 1/8

Let together they can finish the work in x hours.

Part of work done they in one hour = 1/x

$\dfrac{1}{5}+\dfrac{1}{8}=\dfrac{1}{x}$

$\dfrac{8+5}{40}=\dfrac{1}{x}$

$\dfrac{13}{40}=\dfrac{1}{x}$

On reciprocal, we get

$\dfrac{40}{13}=x$

$x=3.076923$

$x\approx 3.08$

Therefore, they will finish the job together in 3.08 hours.

Answer 2

Answer:

1/5+1/10=1/x

(2+1)/10=1/x

3/10=1/x

3*x=10

x=10/3

x=3.333

In 3.333 hours