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How many ways (unordered) can you:
Arrange 10 into groups of 5?
k = | n |
m |
k = | 10 |
5 |
k = 2
a = | n! |
(k!)(m!k) |
a = | 10! |
(2!)(5!2) |
Remember our factorial lesson that:
n! = n * (n - 1) * (n - 2) * .... * 2 * 1
10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2!
a = | 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2! |
2!5!2 |
a = | 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 |
5!2 |
5! = 5 x 4 x 3 x 2 x 1
5! = 120, so we have:
a = | 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 |
1202 |
a = | 1814400 |
14400 |