gmat prep combinations

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Source: — Data Sufficiency |

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by sasi78 » Sat Jun 07, 2008 11:24 pm
This is my explanation

# of groups that have atleast on french teacher = total # of groups possible - # of groups that doesn't have any french teacher

= 10C3 - 6C3 = 120 - 20 = 100.

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by vinviper1 » Mon Jun 09, 2008 7:31 pm
Can you give some more detail? Thanks.

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by netigen » Mon Jun 09, 2008 7:56 pm
Atleast one frechie means the following are the possible combinations

1-French 2-Other OR 2-French 1-other OR 3-French 0-Other

Add up all these possibilities -

4C1 x 6C2 + 4C2 x 6C1 + 4C3

= 4 x 15 + 6 x 6 + 4 = 60 + 36 + 4 = 100

I hope this helps