BOB for Combinatorics

Hi everyone, it's Trinh and the BOB for combinatorics unit.

At first in this unit, i got some troubles because i sometimes misunderstood the questions but now i think i am ok with it.

I think in this unit, we have to read the questions and think about it carefully, remember the pick and choose formula, remember the formula of how to arrange things on a circle and especially for the bracelets and necklaces.

Anyway, good luck on your test guys.
Don't forget your Delicious link..