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15 Aug 2012, 19:25
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35) There are 12 boys and 16 girls in one class, and 15 boys and 14 girls in another. How many ways can a boy-girl pair be chosen, if the boy has to be from one class and the girl from the other?
15 Aug 2012, 21:44
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dualvessilva
The only condition is that the boy and the girl must be from different classes.
Class 1 - 12 boys and 16 girls
Class 2 - 15 boys and 14 girls
You can do it in 2 ways: Pick a boy from Class 1 and girl from class 2 OR pick a girl from class 1 and boy from class 2.
Number of ways of picking a boy from Class 1 and girl from class 2 = 12*14
Number of ways of picking a girl from class 1 and boy from class 2 = 16*15
Total number of ways = 12*14 + 16*15
We are just using the basic counting principle here. Check this link for more: https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/10 ... inatorics/
