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September 18, 2025, 12:17:04 pm
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Author Topic: modulo arithmetic help  (Read 903 times)  Share 

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Martoman

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modulo arithmetic help
« on: April 08, 2010, 01:54:36 am »
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find the last digit in 1! + 2! + 3!... 2010!

I think this smells like modulo stuff.
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TrueTears

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Re: modulo arithmetic help
« Reply #1 on: April 08, 2010, 02:28:18 am »
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think about mod 10
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TrueTears

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Re: modulo arithmetic help
« Reply #2 on: April 08, 2010, 02:36:51 am »
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Another hint: Consider an easier example:

Find the final decimal digit of 1! + 2! + 3! + ... + 10!.

so we got:



So







rest should be a dead giveaway :P
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