Math
posted by Jen
Mary purchased a package of 13 different plants, but she only needed 9 plants for planting. In how many ways can she select the 9 plants from the package to be planted?

Reiny
This would be an example of the C(n,r) that I explained in a few posts below.
You are choosing 9 from the 13, and the order really does not matter, so
C(13,9) = 13!/(9!4!) = 715
look for a key labeled _{n}C_{r} on your calculator
press
13
2ndF
_{n}C_{r}
9
=
you should get 715 
Jen
yea i was having a problem because the calculator i have doesnt have the F button, but thanks for helping me...it was very confusing to me...
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