The Five Penny Problem
Take three coins of the same size (pennies are good because they are thin, avoid £1 coins) and place them such that each coin touches each other coin. This should be trivial as shown below:
However things get more difficult as we add more coins. The challenge is to get 4 mutually touching coins (easy) and 5 mutually touching coins (hard). Answers are below with a gap between them in case you want to check the 4 case without seeing the answer for the 5 case.
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3 coins with the 4th laying on top. Notice that we can't just put one on the bottom to complete the 5 case because the top and the bottom one's would not be touching.
Scroll down for the 5 case...
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Sellotape required for photography purposes. Second angle below.
