SOLUTION: out of 7 books on a shelf how many groups of 3 can be made

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Question 602613: out of 7 books on a shelf how many groups of 3 can be made
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
C(n,r) = (n!)/(r!(n-r)!)

C(7,3) = (7!)/(3!*(7-3)!)

C(7,3) = (7!)/(3!*4!)

C(7,3) = (7*6*5*4!)/(3!*4!)

C(7,3) = (7*6*5)/(3!)

C(7,3) = (7*6*5)/(3*2*1)

C(7,3) = (210)/(6)

C(7,3) = 35

So 35 groups of 3 can be made.