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FoolForMath
Group Title
Just another cute number theory problem:
\((1)\) Find the remainder when \(100!^{100!}+99\) is divided by \(101\).
PS: This problem is posted on request of @Limitless
 2 years ago
 2 years ago
FoolForMath Group Title
Just another cute number theory problem: \((1)\) Find the remainder when \(100!^{100!}+99\) is divided by \(101\). PS: This problem is posted on request of @Limitless
 2 years ago
 2 years ago

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.Sam. Group TitleBest ResponseYou've already chosen the best response.0
Wilson's Theorem?
 2 years ago

FoolForMath Group TitleBest ResponseYou've already chosen the best response.4
Bingo! ^^
 2 years ago

mathmagician Group TitleBest ResponseYou've already chosen the best response.0
first, you should see that 100^k mod 101 is equal to 100, if k is odd and 1 if k is even. The same happens with 100!^k. So, 100!^100!=1mod 101 and 100!^100!+99=100 mod 101
 2 years ago

FoolForMath Group TitleBest ResponseYou've already chosen the best response.4
By Wilson's theorem, \[ 100! \equiv 1 \pmod {101} \] Since \(100!\) is even: \[100!^ {100!} \equiv 1 \pmod {101} \implies 100!^ {100!} +99 \equiv 100 \pmod {101} \] Hence, \(100\) is the remainder. Ref:http://en.wikipedia.org/wiki/Wilson's_theorem
 2 years ago

FoolForMath Group TitleBest ResponseYou've already chosen the best response.4
EDIT: \[ 100!^ {100!} \equiv 1 \pmod {101} \]\[\implies 100!^ {100!} +99 \equiv 100 \pmod {101} \]
 2 years ago

KingGeorge Group TitleBest ResponseYou've already chosen the best response.0
You don't even need Wilson's Theorem for this. Since \(100!\) is a multiple of \(100\), and coprime to 101, we have that \(100!^{100!}\equiv1\pmod{101}\) by Fermat's Little Theorem. Hence, \(100!^{100!}+99\equiv100\pmod{101}\).
 2 years ago
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