A train travels 60 miles in 60 minutes. For the first 30 miles, it traveled at 30 miles per hour. What must its average speed be for the remaining 30 miles to complete the trip on schedule?
90 miles per hour
The train used all 60 minutes on the first 30 miles (30 miles at 30 mph takes 60 minutes). Wait, that breaks the premise. Let's fix: A train travels 60 miles. It travels the first 30 miles at 30 mph. How fast must it travel the next 30 miles to average 60 mph for the whole trip?
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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