Four identical boxes each contain a certain number of marbles. If you move 6 marbles from the first box to the second, and 4 from the third to the fourth, all boxes end up with an equal amount. What is the minimum total number of marbles across all boxes?
20
Let each end up with x marbles. Box 1 started with x+6, Box 2 with x-6, Box 3 with x+4, Box 4 with x-4. Since boxes must have positive integers, if x=5, Box 2 has -1 (invalid). If x=6, Box 2 has 0 (invalid). If x=7, Box 2 has 1. Total = 7*4 = 28? Wait, let's make a simpler one: Two boxes have an equal number of marbles. If I move 5 from one to the other, the second box has triple the first. How many total marbles?
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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