SFF! Solve For Fun

( 158 64 ) {158 \choose 64} mod 3 3


The answer is 1.

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3 solutions

Sai Yaswanth
Nov 13, 2014

64=1mod3 so when 64 is raised to any power it is 1 only

guess 0 , 1 , or 2

everyone attempted this must be correct

math man - 6 years, 7 months ago

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Yes only guessing can work but probability that your guess is correct at first attempt is 1 3 \frac { 1 }{ 3 } .

shivamani patil - 6 years, 7 months ago

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It reduces to 2 options as we can see that the denominator divides 75 powers of 3 and so does the numerator so the answer can't be 0.

Kushagra Sahni - 5 years, 2 months ago

We get 3 attempts too!

Mr. India - 2 years, 3 months ago

Pls explain?

shivamani patil - 6 years, 7 months ago

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64 i s congruent to 1 mod 3 it means when u divide 64 with 3 remainder is 1 so when 64 is raised to any power it is also congruent to 1 mod 3

Sai Yaswanth - 6 years, 7 months ago

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But it is 158 ! ( 158 64 ) ! 64 ! = 158 ! 94 ! 64 ! \frac { 158! }{ \left( 158-64 \right) !64! } =\frac { 158! }{ 94!64! } .

shivamani patil - 6 years, 7 months ago

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@Shivamani Patil thanks for your response

Sai Yaswanth - 6 years, 7 months ago
Joshua Lowrance
Nov 11, 2018

There are only three possible values in m o d 3 \mod3 : 0 0 , 1 1 , and 2 2 . Because you have three tries to get this right, you can just try all three, and you will be right for one of them (I know, I know, it's cheating)

Shivamani Patil
Nov 13, 2014

Use luca's theorem.

what is lucas theorem can u explain it

Sai Yaswanth - 6 years, 7 months ago

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You can check wiki which i wrote in number theory section.

shivamani patil - 6 years, 7 months ago

Use python -_- . 2 seconds of code :# :3

Krishna Ar - 6 years, 7 months ago

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https://brilliant.org/wiki/lucas-theorem/?subtopic=modular-arithmetic&chapter=modular-arithmetic#lucas-theorem

shivamani patil - 6 years, 7 months ago

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Yes, yes.............you're right.

Krishna Ar - 6 years, 7 months ago

"even you python'ed"

Kartik Sharma - 6 years, 7 months ago

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Yes, But I can't believe that you did so @Kartik Sharma

Krishna Ar - 6 years, 7 months ago

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