FIND THE REMAINDER

Find the remainder when 1!+2!+3!+............+100! is divided by 24


The answer is 9.

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2 solutions

Rishabh Jain
Jun 22, 2014

just add 1!+2!+3! =9 because other numbers will be divisible by 24 so the answer is 9 \boxed{9}

That is cool

Jared Beaufait - 4 years, 4 months ago
Nicolas Bryenton
Jul 17, 2014

Notice that 4 ! = 24 4!=24

Then clearly, 4 ! 0 ( m o d 24 ) 4! \equiv 0 (mod 24)

Therefore for any n! where n is greater than 4, n! will have 24 as a factor and therefore leave no remainder when divided by 24.

It follows that 4 ! + 5 ! + 6 ! + . . . + 100 ! 0 ( m o d 24 ) 4!+5!+6!+...+100!\equiv 0(mod24)

And then all that is left over is 1 ! + 2 ! + 3 ! = 9 1!+2!+3!=9

The remainder, therefore, is 9 \boxed { 9 }

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