are concerned with figuring the total number of
possibilities regardless of order or sequence.
- Example:
How many different combinations of 3 letters of abcd (4
letters) can we make?
- abc abd acd bcd. There are four.
- We can write these down as we did above but when there are lot of
possibilities it becomes very complicated. So lets discuss a way to find
any number of combinations.
4.3.2 =
24 = 4 our answer
- 3.2.1 = 6
is the number of letters we started with and
then we the multiplied it by 3 and 2 -- we went
3 places down ---the
number in each group
We then divided by 3---
is the number of letters is each combination -- we multiplied this down to
1.
- There are 10 men available to make up 3 men teams. How many 3 men
teams can we make up?
- 10
(9)(8) = 720
120
- 3
(2)(1)
6
- 10
is the number of men available
- multiplied 10 X 9 X 8 we went
3
places down ---the number of men on each team
- we divided by
3
(the number on each team) then time 2 and 1. We always bring it down to 1.