1.29.10

As we talked about in class, the difference between the number of arrangements when order matters and the number of arrangements depends on how many items you are choosing at once.  When you are choosing 2 items at once, you divide by 2 to find the number when order doesn’t matter.  If you are choosing 3 items, you divide by 6.  If you are choosing 4 items, you divide by 24.

Answer the following questions in about one page (typed):

What is the significance of these numbers?

How do they relate to the situation?

How can you predict how many arrangements there will be for any situation (when order doesn’t matter)?

Hint:  How many ways are there to arrange 2 different items (A and B, for example)?  How many ways are there to arrange three different items (such as A, B, and C).  How many ways are there to arrange four items (such as A, B, C and D)?