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Calculate the digit in the unit's place of the number 2! + 3! +...........99! .

 Jun 13, 2020
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The key to this problem is realizing that factorials past 5! have a units digit of 0. (Make sure you see why)

Therefore, we only have to look at 2! + 3! + 4! = 2 + 6 + 24 = 32

So the units digit is 2.

 Jun 13, 2020

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