Question

Number Theory problem!

Answer 1

Find the last 3 non-zero digits of 2015! .

Answer 2

this mean 2015 factorial ? so yes

like an idea than you multiply 5 by 5 how many get ? hope little help you

Answer 3

Nice idea!
So this will help me to find the numbers of trailing zeros in 2015! which is equal to the exponent of 5 in its factorization which is:

\([\frac{2015}{5}]+[\frac{2015}{5^2}]+[\frac{2015}{5^3}]+...=403+80+16+3=502\)

Am I rite?

Answer 4

No

Answer 5

T_T

Zarkon,can u show me how u do it?

Answer 6

I don't know of a quick way to do this. You need to eliminate all powers of 5 in 2015! and a corresponding number of 2's. You could write a computer code to do it.

Answer 7

@BRANIAC DO YOU SEE indifferent how many time you multiply 5 by 5 allways will get the last number 5 - hope little help

Answer 8

Competitive coding?

Answer 9

Alright,zarkon.
I found a calculator that can calculate big values,lol.

Yes,I do,jhonny9.
It seems that everytime you keep on multiply 5 by 5,u will always get the last number 5.

Nope,imqwerty.
Mathematics. ^

Answer 10

you don't need to compute large values if you program it correctly

Answer 11

I found another solution..hold on,I will post those workings here ^

Answer 12

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