In the UK, 1p, 2p and 5p coins have thicknesses of 1.6mm, 2.05mm and 1.75mm respectively.
Using only 1p and 5p coins, Joe builds the shortest (non-empty) stack he can whose height in millimetres is equal to its value in pence. Penny does the same but using only 2p and 5p coins.
What is the value of each stack?
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Hamilton Mathematical Olympiad 2020 (2020)
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