Combination and Permutation

Soo, this week we are going to go over some stuff about combination and permutation. You will normally have to use this stuff in word problems when trying to figure out different ways to do stuff.

Permutation is used when you need to find out how many different ways something can be ordered when order is important! The formula for Permutation is:

• nPr = n!/(n-r)!

Combination is used when you need to find out how many different ways something can be ordered when order is NOT important! The formula for Combination is:

• nCr = n!/(n-r)!r!

Now i'm going to work a problem using each.

Example 1. In how many ways can a club with 20 members choose a president and a vice president?

1. Because vice president and president are two different things, order IS important.
2. Use the Permutation formula to solve this problem.
3. 20!/(20-2)!
4. 4Your answer would be 380.

Example 2. In how many ways can the same club as above choose a two person governing council?

1. Because it is not a specific governing council, order is NOT important.
2. Use the Combination formula to solve this problem.
3. 20!/(20-2)!r!
4. Your answer would be 190.

That's about it for now,

Carleyyy(: