You are in a dank, dark, dungeon, awaiting execution for crimes against logic puzzles.
Luckily, you have a chance to redeem yourself. You must play a logic puzzle with the gaoler, and if you win, you go free. The game you must play works like this:
The Gaoler will put a blindfold on you. Then, on a flat table in your cell, the gaoler will place 101 identical coins, which on one side have the Queen's head, and on the other side have the Queen's coat of arms. He will ensure that 21 of the coins are showing the Queen's head, and 80 are showing the Queen's coat of arms.
The challenge you face is to choose 21 coins from the 101 coins on the table by picking them up and placing them flat on the table in front of you, while the other 80 remain in front of the gaoler.
Once you have chosen your 21 coins, and placed them flat on the table in front of you, the gaoler will remove your blindfold. If the Gaoler's 80 coins show more Queen's heads than your 21 coins, your execution will proceed immediately. Otherwise, you go free.
Remember, you are blindfolded, and the pattern on each side of the coins is too similar to tell apart by touch. Oh — and you only have five minutes to make your choices.
1. What strategy maximises your chance of gaining your freedom?
2. Using this strategy, how likely are you to gain your freedom?
As usual, answers in
please, so everyone can have a go.
(I've seen this puzzle in a couple of places, but most recently here: http://www.nickyee.com/index-puzzles.html )