Combination vs Permutation

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Combination vs Permutation

by nhai2003 » Sun Jun 21, 2009 4:09 am
A second grade class is writing reports on birds. The students' teacher has given them a list of four birds they can choose to write about. If Lizzy wants to write a report that includes two or three of the birds, how many different reports can she write?

Guys please help me with this one.
I have no idea how to solve it.
Thanks!

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by Neo2000 » Sun Jun 21, 2009 7:42 am
In this case, its a Combination, since Lizzy only needs to select the birds

Select 2 birds = 4C2
Select 3 birds = 4C3

Total number of ways of writing a report by selecting 2 or 3 birds = 4C2 + 4C3