Bob runs 6 miles per hour. His friend Jim runs at 9 miles per hour. If Bob has a 1 mile head-start, how many minutes will it take before Jim catches him?
Bob runs .1 miles per minute because 6 / 60 = <<6/60=.1>>.1
Jim run at .15 miles per minute 9 / 60 = <<9/60=.15>>.15
We know that .1(Number of Minutes) + 1 = .15(Number of Minutes)
Therefore 1 = .05(Number of minutes)
Therefore (Number of minutes) = 20 because 1 / .05 = <<1/.05=20>>20
#### 20