
A man sits blindfolded at a table with 20 coins laid out in front of him. He does not know the layout of
the coins, only that ten are heads and ten are tails. He has a pair of gloves on and while he can feel
where the coins are, he can't feel whether they are heads or tails. His task is to create two groups of
coins, each having the same number of heads and tails. He may only move or flip coins. How can he
accomplish this (while remaining blindfolded)?
ANSWER:
By creating two groups of ten coins, then flipping over the coins in one of
the groups.
EXPLANATION:When you split the coins into two groups of ten, the first group will have
x heads and
10 - x tails and the second group will have
10 - x heads and
x tails. You can test this by plugging in 0, 5, or 10
for the value of
x. By flipping over the coins in the second group, heads become tails
and tails become heads so there'd be
x heads and
10 - x tails
(the same as in the first group).
Do you have a
suggestion for this puzzle (e.g. something that should
be mentioned/clarified in the question or solution, bug, typo, etc.)?