Modular math?

[alexjohnson16]

Ran across a problem on one of my quizzes that says to figure out (-9x12)(mod 4). Can someone show me how to do this? Or show me another problem that shows how to do it?

I searched the notes and can't find anything at all.

 

[reverend boltron]

think about 14%5..

which is 14 mod 5, which is basically integer division, where you take the remainder, instead of the quotient.

so.. 14%5 is like 14/5 = 2 REMAINDER 4.. you keep the remainder 4.. answering 4.

 

[TuxDave]

Do you know how to do mods in general? Like 4 mod 3? If so, then you can reduce the problem above by rewriting it as:

(-9x12)mod4 to (-9x3x4)mod4 to ...... the answer.

 

[alexjohnson16]

Need to relearn multiplication before I learn this crap.

 

[reverend boltron]

-108%4 = 0 not -27.. -108/4 = -27.. but yes.. the answer would be 0

 

[alexjohnson16]

Nvm: I'm a douchebag and can't multiply right. I got it now. Thanks guys.

 

[reverend boltron]

Well, I'm right about the modular math with the numbers that I'm working with. You asked if -108 mod 4 = 0, and that is correct.

first link on a google search "modular math"

go through it, it seems pretty cool. there are more pages than just the first, its like a tutorial for modular math.