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'Making 11p' printed from https://nrich.maths.org/
11
With no 5p coins, there could be 0, 1, 2, 3, 4 or 5 2p coins,
i.e. 6 possible ways.
With one 5p coin, there could be 0, 1, 2 or 3 2p coins, i.e. 4
possible ways.
With two 5p coins, there can be no 2p coins, i.e. 1 possible
way.