Permutation questions- urgent help needed

pckeller
Wed, 23 Jan 2013 11:06:27 +0000

If you do know nCr…

It’s 4C1 x 4C2

But you could also call the plumbers A, B, C, D and the trainees p, q, r, s…

When you do problems by listing, be organized and you will save time.

For example, after listing Apq, Apr, Aps, Aqr, Aqs and Ars, you can just take those 6 and multiply by 4.

As for the other one I gave you about the two letter codes, I got more than 32…but maybe I did it wrong :)