You can put this solution on YOUR website! Assuming that they are all different CDs, think about it this way:
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There are 9 ways to pick the first CD, then once you have done that, there are 8 ways to pick the second CD, 7 ways to pick the third one, and so on.
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So the expression is: . Mathematicians have a shorthand way to write that sort of expression: 9! (read 9 factorial).
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I'll let you do the calculator work, or if you have MS Excel on your computer, you can type =fact(9) into a spreadsheet cell and you'll get your answer.
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Hope that helps,
John
