Here’s a riddle that someone just sent me, that I liked. Note to Dr. Pepper – please don’t figure it out right away!
You are sitting at a table with 100 pennies on it. You are blindfolded, and told that 90 of the pennies show heads, and the other 10 show tails. You have to split the pennies into two piles, such that the two piles each have the same number of tails. It does not matter if the two piles have the same number of pennies; it only matters that the number of tails must be the same. Assume that you cannot distinguish between heads and tails by touching and feeling the coins (e.g. they are paper cut-out pennies from a kid’s play money). How do you do this?