A train leaves Chicago traveling 60 miles per hour. Another train leaves the same station two hours later traveling 90 miles per hour in the same direction. How many hours after the *first* train leaves does the second train catch up?
6 hours
In 2 hours, the first train travels 120 miles. The second train closes the gap at a rate of 90 - 60 = 30 mph. To cover 120 miles, it takes the second train 120 / 30 = 4 hours of travel time. Since the second train left 2 hours after the first, it takes 4 + 2 = 6 hours total since the first train left.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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