Multiplication Shortcut

I remember in 5th grade my teacher showed us a shortcut used to quickly multiply certain numbers.  I believe it was multiplying two double digit numbers.  Well, she ended up saying that it didn't work past 19 or something along those lines.  So one day after I finished my class work, I just stood at the board and screwed with it until I figured a way to do it past 20, past 30, past 40, etc.  Her words of thanks?  "Ok."  So I basically thought "screw you" to the whole method and forgot about it that week.  On an unrelated note, I'm pretty sure that instant was the one that killed my love for school.

Anyway, I'm bringing this up because I was hoping some of you might have been taught a similar shortcut method, and I might be able to use it to figure out what exactly I did.  I mean, I don't need to do it now, but it was still something that I felt I had accomplished and I would like to remember it again.  Any help?

Punch it in a goddamn calculator.

rly, they're like 4 bucks now

What'dya want?  A cookie?

Actually, some teachers suck, and will feel threatened when their students might be smarter than them.

There is a well known story about a primary school teacher that punished their students by making them add the numbers 1 to 100.  Until one student figured out that (1+100)+(2+99)+(3+98)+...+(50+51) = 50*101
Supposedly, it was Gauss.

I'm guessing this has something to do with the method used.
(a+b)*(c+d) = (a+b)c + (a+b)d = ac + bc + ad + bd

Can you remember?

Cockpenis.

>>4
Yaah it was Gauss. Fucking genius.

>>2
start -> run... -> type "calc" -> ok

>>4
Yaah it was Einstein. Fucking jew.

JEWS ARE STUPID