CPM Homework Help : GB8I Problem 11-118

Robby Robot can make a widget in 7 minutes. With the help of Roger Robot, the job can be done in 4 minutes. How long would it take Roger Robot working alone?

Hint:

Let $x =$ the number of minutes for Roger Robot to complete the job.

Robby Robot will make $\frac{1}{7}$ of a widget per minute and Robby will make $\frac{1}{x}$ of a widget per minute.

Write and solve an equation using the format work rate · time = 1 job

Hint (2):

They are working together, so the total work rate is $\left(\frac{1}{7}+\frac{1}{x}\right)$