Memorization

[chrishuff]

Is there some easy way to memorize the difference between the following:

Centroid, Circumcenter, Incenter, Orthocenter, and Midcenter of a triangle? [Looked off of #5 on the 2010 District 1 Test]

[nsguy1350]

Not really, I got the hang of it after a while without hard memorization.

First off, midcenter does not exist.
Centroid is medians. (from angle vertex to midpoint of opposite side)
Orthocenter is altitudes. (forms right angle with opposite side)
Circumcenter is perpendicular bisectors. (passes through midpoint of side, and is perpendicular)
Incenter is angle bisectors. (cuts angles in half)

I don't see any easy mnemonic techniques for that, but it is definitely worth knowing.

[chrishuff]

Now how about for the types of numbers? I have made a bunch of flashcards to look over (Although I admit, most of the time I look at them, were right before competition) and my strategy hasn't been working out too well.

[nsguy1350]

I typed this up... they are kind of hard to remember, but with practice, you can get them.
http://www.dentonisd.org/51233829152830 ... 6&C=110089

Some observations: odd abundant numbers are rare; 945 is the smallest one.
Memorize perfects as 6,28,496,8128.
Notice how I grouped the numbers together, to make it easier to identify which belong with which.