SOLUTION: I need to calculate how many different groups of 3 I can make out of a total of 15, eg 1,2,3 or 1,14,15. Is there a formala that allows me to do this, if so what type of formula

Algebra ->  Test -> SOLUTION: I need to calculate how many different groups of 3 I can make out of a total of 15, eg 1,2,3 or 1,14,15. Is there a formala that allows me to do this, if so what type of formula       Log On


   

Question 574528: I need to calculate how many different groups of 3 I can make out of a total of 15, eg 1,2,3 or 1,14,15.
Is there a formala that allows me to do this, if so what type of formula is it.
Thanks
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Use the combination formula

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

C(15,3) = (15!)/(3!*(15-3)!)

C(15,3) = (15!)/(3!*12!)

C(15,3) = (15*14*13*12!)/(3!*12!)

C(15,3) = (15*14*13)/(3!)

C(15,3) = (15*14*13)/(3*2*1)

C(15,3) = (2730)/(6)

C(15,3) = 455

So 455 different groups can be made.