# Thread: MEGSSS help?

1. ## MEGSSS help?

I am in 6th grade MEGSSS (advandced math) and I don't really understand tonight's homework. The teacher gave us modulo 7 multiplication. I have no idea what that is. If it helps, the first problem is $\displaystyle 5$x$\displaystyle 3$ (modulo 7).

2. Just multiply the numbers as you would normally and then figure out the least residue (remainder) modulo 7:
$\displaystyle 5 \cdot 3 \equiv 15 \equiv 1 \ (\text{mod }7)$

3. I'm not sure whether in 6th grade you'll know about the meaning of "residue class"
Originally Posted by Epicusername
I am in 6th grade MEGSSS (advandced math) and I don't really understand tonight's homework. The teacher gave us modulo 7 multiplication. I have no idea what that is. If it helps, the first problem is $\displaystyle 5$x$\displaystyle 3$ (modulo 7).
Working modulo 7 means that whatever result you have, you work with the remainder of this result in the Euclidian division by 7.

Since 15=7x2+1, its remainder in the Euclidian division by 7 is 1.
Thus $\displaystyle 15 \equiv 1 \bmod 7$

Basically, if $\displaystyle a \equiv b \bmod c$, then c divides a-b.