Thread: Permutations and combinations

There are five members of the Math Club. In how many ways can the positions of officers, a president, and a treasurer, be chosen? I thinked it's just 5 factorial. But the answer is 20. Which means they divided by 3 factorial... Why ?

You have two offices (President, Treasurer). Now you have to choose 2 people from a group of 5 how many ways can this can be done.

Spoiler:

In ways. Multiplication by two is to allow permutations among them. Thanks to Evgeny (emakarov) for the correction.

Originally Posted by Shwems

There are five members of the Math Club. In how many ways can the positions of officers, a president, and a treasurer, be chosen? I thinked it's just 5 factorial. But the answer is 20. Which means they divided by 3 factorial... Why ?

See k-permutations.