In this previous post, I proposed a new way of counting things. If you haven’t already read it, please do so. Otherwise this post won’t make much sense.

In that post I ended with the following problem…

How many rectangles are in this 3-by-4 figure?

I promised you an answer to this problem, so here it goes…

For each new rectangle added to the grid, I record the number of NEW rectangles that result. Then I add up all the values.

So there you have it…60 rectangles are in the 3-by-4 grid.

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