Question

What is the probability of winning a lottery in which you must choose 6 numbers from the numbers 1 through 13?

a) Assuming that order is unimportant.
b) Assuming order is important.

Answer 1

The formula for combinations (how to choose r things from a larger set of n things) is:

Answer 2

So for part "a" we have

13! / 6!*(7!) =

13* 12* 11* 10* 9 * 8* 7! / 6!*7! =

13* 12* 11* 10* 9 * 8 / 6 * 5 * 4 * 3 * 2 =

13* 11* 2 * 3 * 2 =

1,716

and to check that, here's a combination calculator:
http://www.1728.org/combinat.htm

Answer 3

should we assume duplication is not acceptable?