SOLUTION: If a person can select 7 presents from 12 presents under a Christmas tree, how many combinations are there?

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Question 1086772: If a person can select 7 presents from 12 presents under a Christmas tree, how many combinations are there?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Use the Combination Formula (n C r). In this case, the number of items selected is r = 7 and this is from a pool of n = 12 items total.

n C r = (n!)/(r!(n-r)!)

12 C 7 = (12!)/(7!*(12-7)!)

12 C 7 = (12!)/(7!*5!)

12 C 7 = (12*11*10*9*8*7!)/(7!*5!)

12 C 7 = (12*11*10*9*8)/(5!) ... note how the 7! factorial terms cancel

12 C 7 = (12*11*10*9*8)/(5*4*3*2*1)

12 C 7 = (95040)/(120)

12 C 7 = 792

Answer: 792

Order does NOT matter.