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November 26, 2015

100 Coins Puzzle

You have a 100 coins laying flat on a table, each with a head side and a tail side. 10 of them are heads up, 90 are tails up. You can't feel, see or in any other way find out which side is up. Split the coins into two piles such that there are the same number of heads in each pile.

6 comments:

Anonymous said...

Split the coins in half. They all have heads.

David and Anne lymn said...

make two piles of 50 coins each. There are 50 heads in each, some pointing up and some pointing down to the table

Unknown said...

Split into one pile of 10 and another of 90. Flip every coin in the smaller pile over. If the original pile of ten had 0 heads, then it now has 10. This matches the pile of 90. And so on for all the other cases of heads from 1 to 10.

larry atkinson said...

Split into one pile of 10 and another of 90. Flip every coin in the smaller pile over. If the original pile of ten had 0 heads, then it now has 10. This matches the pile of 90. And so on for all the other cases of heads from 1 to 10.

kpm said...

If you are picky with the wording of the problem, which is sometimes the way to get a solution, it only asks that there are an equal number of heads in each pile, not an equal number of "heads up" in each pile...so 50 each in two piles will result in 50 heads in each pile, some will be up and some will be down...

Not sure if this was the intention of the problem, but following the exact wording, this is a solution.

Jerry Critter said...

I think larry's got it...without any word smithing.