I just started doing some AMC questions out of a problem-solving book that was lying around my house. I was wondering if you could advise me on how to approach these problems, and give me a hint on this one. The problem I have been facing lately is that even though the solutions look really obvious once I actually read them, I'm completely lost when it comes to solving them on my own. Anyway, here is the problem.
Suppose that the base-8 representation of a perfect square is ab3c, where a is not equal to 0. What is c?