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10 Choose 3 = 120

There are 120 ways to choose 3 items from 10 when order does not matter. It is the standard classroom example: forming a 3-person committee from 10 students.

Combinations (10C3)
120
Permutations (10P3)
720

How 10 choose 3 is calculated

The combinations formula is C(n, r) = n! / (r! × (n − r)!). Substituting n = 10 and r = 3 gives:

C(10, 3) = 10! / (3! × 7!)
         = 720 / 6
         = 120

The 7! in the denominator cancels all but the top 3 factors of 10!, so 10 choose 3 is the product of 3 descending terms starting at 10, divided by 3!. That product, 720, is the number of ordered arrangements (10P3); dividing by 3! = 6 removes the duplicate orderings and leaves 120.

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