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how many unique 10 digit numbers can be formed if the number 2 is in the first place and repetition is allowed?

 

 Aug 6, 2020
 #1
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xxxxxxxxxxx

 Aug 6, 2020
edited by Guest  Aug 6, 2020
 #2
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10 digit numbers go something like this: _ _ _ _ _ _ _ _ _ _ 

If number 2 is in the first place, it's kind of set so you basically only need to find 9 digit numbers now: _ _ _ _ _ _ _ _ _

If repition is not allowed, the first digit has 9 (no 0) choices the second also has 9 (because any number except the first chosen) the third has 8, and so on. That's basically going to be 9*9! (without the 1 but anything times 1 does nothing)

Try figuring that out!

 Aug 6, 2020

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