MathDB
Bicycles and trains

Source: 2014 AIME I Problem 4

March 14, 2014
AMC

Problem Statement

Jon and Steve ride their bicycles on a path that parallels two side-by-side train tracks running in the east/west direction. Jon rides east at 20 miles per hour, and Steve rides west at 20 miles per hour. Two trains of equal length traveling in opposite directions at constant but different speeds, each pass the two riders. Each train takes exactly 1 minute to go past Jon. The westbound train takes 10 times as long as the eastbound train to go past Steve. The length of each train is mn\tfrac mn, where mm and nn are relatively prime positive integers. Find m+nm+n.