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Jane likes to wear 3 bracelets, each a different color. If she has 8 bracelets each of a different color, how many combinations of 3 different-colored bracelets can she select to wear?
Combination problems involve choosing r combinations from n items. In this case, n = 8 bracelets and r = 3 bracelets
The formula for a combination of choosing
r unique ways from n possibilities is:
where n is the number of items and r is the unique arrangements.
What is n!, r!, (n - r)!?
n! signifies a factorial. n!, for example is shown in our
factorial lesson as being n! = n * (n - 1) * (n - 2) * .... * 2 * 1
Plugging in our factorial numbers, we get:
Calculate the numerator n!: n! = 8!
8! = 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
8! = 40,320
Calculate the first denominator (n - r)!: (n - r)! = (8 - 3)!
(8 - 3)! = 5!
5! = 5 x 4 x 3 x 2 x 1
5! = 120
Calculate the second denominator r!: r! = 3!
3! = 3 x 2 x 1
3! = 6
Now calculate our combination value nCr for n = 8 and r = 3:8C
3 =
56Therefore, there are 56 unique ways to choose 3 different color bracelets from 8 total bracelets