Question. 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?
Answer. 20
What step-by-step reasoning justifies that answer?
Reasoning: Bob runs .1 miles per minute because 6 / 60 = .1. Jim run at .15 miles per minute 9 / 60 = .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 = 20.