Hourglass Problem
Sunday, July 15, 2007 at 10:02AM
Emma A Holliday

hourglass.jpgProblem

You have two hourglasses. One empties in 7 minutes, the other empties in 4 minutes. How can you use these two hourglasses to measure exactly 9 minutes?

Answer

???

Picture from: http://www.lacrossemccormick.com/products/hourglass/hourglass.jpg

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