Answer: 24 minutes
Step-by-step explanation: To solve this kind of a problem which is called a work problem, it's important to understand the following idea.
Since Elam can wire a light in 40 minutes, we know that in 1 minute,
Elam can wire 1/40 of the light and in 2 minutes, Elam can wire 2/40 of it.
Therefore, in t hours, Elam can wire t/40 of the light.
The same applies for Michael, in t hours, he can wire t/60 of the light.
So to solve the problem, we use the following formula:
Part of job done by Elam + part of job done Michael = 1 job done
The part of the job done by Elam is t/40 and t/60 for Michael.
So we have t/40 + t/60 = 1.
Now multiply both sides by 120 to get 3t + 2t = 120
or 5t = 120 so t = 24.
So it takes 24 minutes if they work together.
