Hey everyone. I would like to urge all sdners who are studying for the dat, specifically Qr section, to please post any Qr problems, no matter how simple or complex they are. A lot of people have posted over the past week and I think its helping a lot of people, including myself :D. I'll begin.

How many 3 letter license plates can be formed from the letters A, B, C, D, E, F, if each letter is to be used only once. This is an easy problem to do mechanically. (6x5x4). My question is a little deeper.

This is a permutation because by definition the order matters. I can't figure out why the order matters. How did you guys decipher that the order matters. Is the key phrase here that "each letter is to be used only once"?

Thanks

Have you ever seen a license plate where ABC is the same as CBA?

well answered. The way that you know that it is permutations and not combnations is by just reading the question and thinking a little, not every question is all math and formulas. Thinking before you solve every question is very important.