- #1

Chicago_Boy1

- 6

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I am going through some sample problems exercises in Paul Sally's

*Tools of the Trade*, and am being asked to prove the Fundamental Counting Principle. That is,

*If A has m elements and B has n elements, then A X B has mn elements.*

Sally goes on to write that "this is simple to prove by drawing little trees or using some other artifice."

Basically, I am not really sure what he means by "drawing little trees." Can someone guide me through how I can actually prove this WITHOUT induction?

Thank you in advance.

P.S. I know that I am supposed to show that I've attempted to solve the problem, but honestly I have no idea where to even start.