I am dealing with sets of problems that go as such: "How many n-cent postages can be formed from x and y cent stamps"(adsbygoogle = window.adsbygoogle || []).push({});

For instance, I am doing a problem where x and y are 4 and 11 respectively. I don't understand how to determine a base case. I know that I must proof P(k + 1) for all P(i). The answer in my book is that the base case is a postage equal to 30 cents, but I don't follow. Could someone explain how I would go about finding a base case? The book seems to set this bound after showing 4 and 11 cent combinations up to 28. However, I do not see why 30 was chosen as a lower bound. Thanks.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Base Case in Strong Induction Proofs

**Physics Forums | Science Articles, Homework Help, Discussion**