Monday, November 16, 2009

Please help me with my math homework.?

I'm having a brain-fart. D; I can't remember how to do this kind of stuff. Help please?





Find the number of combinations.


1. Ways to choose 4 different flowers from the following kinds: rose, tulip, daisy, petunia, sunflower, begonia, lilac, orchid


2. Ways to choose 6 different baseball cards from 25 baseball cards


3. Ways to choose 5 different magazines from 34 magazines

Please help me with my math homework.?
1. 8*7*6*5


2. 25*24*23*22*21*20


3. 34*33*32*31*30
Reply:1.) 8 choose 4





( 8 )


( 4 ) sorry it looks bad I hope you realize the are one big set of paranthesis.





Many teachers will accept this if not it is equal to


8 * 7 * ... (8 - 4) + 1


------------------------


4 * 3 * ... 1





Obviously the the ellipses are trivial here but the formula says multiple the top four number and divide by the bottom four:





8 * 7 * 6 * 5


---------------- = 70 ways to chose flowers


4 * 3 * 2 * 1








2.) 25 choose 6 or


(25)


( 6 ) = top 6 / bottom 6


25 * 24 * 23 * 22 * 21 * 20


------------------------------------ = 177100 ways to choose bbcards


6 * 5 * 4 * 3 * 2 * 1








3.) 34 choose 5


(34)


( 5 ) =


34 * 33 * 32 * 31 * 30


------------------------------ = 278256 ways to choose 5 mags


5 * 4 * 3 * 2 * 1





Check my math.


Hope this helps! :)
Reply:Previous poster is using the formula for permutations. You need the formula for combinations, which I'm sure is right in your book. SInce order doesn't matter, you have to correct for the fact that say rose, tulip, daisy, petunia is the same as petunia, tulip, daisy, rose.





The first one has 70 possibilities. Get your formula and figure out why.


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