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Fast food

by Baldini » Thu Mar 12, 2009 6:10 am
A fast food company plans to build 4 new restaurants. If there are 12 sites that satisfy the company's criteria for location of new restaurants, in how many different ways can the company select the 4 sites needed for the new restaurants if the order of selection does not matter?

a. 48
b. 288
c. 495
d. 990
e. 11880

OA is C

Can someone please explain why is it not a simple case of 12C4?

Thanks in advance
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Re: Fast food

by Ian Stewart » Thu Mar 12, 2009 6:22 am
Baldini wrote: Can someone please explain why is it not a simple case of 12C4?

Thanks in advance
It is as simple as you think: 12C4 is equal to 495.

12C4 = 12!/(8! * 4!) = (12*11*10*9)/(4*3*2*1) = (11*10*9)/2 = 495.
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