How many ways can you make change: Some easy proofs
Abstract
Given a dollar, how many ways are there to make change using pennies, nickels, dimes, and quarters? What if you are given a different amount of money? What if you use different coin denominations? This is a well known problem and formulas are known. We present simpler proofs in several cases. We use recurrences to derive formulas if the coin denominations are 1,x,kx,rx, and we use a simple proof using generating functions to derive a formula for any coin set.
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