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## Ask Professor Puzzler

Do you have a question you would like to ask Professor Puzzler? Click here to ask your question!

Shawna from Michigan asks, "The upper case sigma symbol is used for summation, but I've also seen the upper case pi symbol used in a similar way. What does that mean?"

Hi Shawna. The answer is pretty short and straight-forward. The pi symbol, when used that way, means multiplying a set of numbers (instead of adding them).

If you're wondering why pi is used, the reason is simple; it's the same reason we use sigma for sums. S for sigma, S for sum. P for Pi, P for product.

Here's an example; take a look at this expression:

This means that we multiply together all the numbers we get by plugging in x = 3, x = 4, x = 5, and x = 6.

The numbers are:

3 - 2 = 1
4 - 2 = 2
5 - 2 = 3
6 - 2 = 4

So the product is 1 x 2 x 3 x 4 = 24

Of course, that was a fairly simple problem, and they can get a lot more complicated (interesting) than that. But that will be sufficient to answer your question, I think!

Professor Puzzler

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