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Answer to Coin Puzzle

For those stumped or wanting to check their answers, read on to see the solution to Friday's coin puzzle.

All Billy needs to do is to split the coins into two piles, one with 40 coins and one with 60 coins and then flip over all of the coins in the pile of 60. Note: if all of the heads-up coins are in the pile of 60 then both piles now contain zero heads. In general, for every tail in the pile of 60 there is a head in the pile of 40. If the pile of 60 contains x tails, then the pile of 40 contains the remaining (40-x) tails and x heads. When Billy flips all of the coins in the pile of 60, he turns the heads in that pile to tails, and tails to heads, so both piles will end up with exactly x heads.

Comments (1)

Cray:

shouldnt he be flipping the smaller pile? That makes much more sence.

for e.x: 0x in the 60 pile means 40x in the 40 pile. flip the 40 pile over and you got 0x in both. same goes for 1x, 2x, etc.

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