Suppose marcus delivers papers at a rate of 9 papers in 18 minutes. How much longer would it take him to deliver 100 papers than 72 papers? Justify your response.

We need to write the following expression and solve for x:

9/18 = 100/x

So: 9x = 1800

x = 200

So it would take him 200 minutes to deliver 100 papers.

We do the same for 72 papers

9/18 = 72/x

so 9x = 1296

and x = 144

It would take him 144 minutes to deliver 72 papers.