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Find the last two digits of the following sum: 5! + 6! + 7! + 8! + 9! + 10! + ... + 100!

 Jun 9, 2022
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10!  and  any greater integer factorial   will always end in two zeroes

 

So.....

 

5! =        120

6! =        720

7!  =     5040

8!  =   40320

9! =  362880

 

So......  the sum has the last two digits =     20 + 20 + 40 + 20 + 80  =   _80

 

 

cool cool cool

 Jun 9, 2022
edited by CPhill  Jun 9, 2022

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