如何计算Combinations
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Combinations count the number of ways to select k items from n items without regard to order. Written as C(n,k) or "n choose k", used in probability and statistics.
公式
C(n,k) = n! / (k! × (n-k)!)
分步指南
- 1Enter n (total items) and k (items to select)
- 2Calculate factorials n!, k!, and (n-k)!
- 3Divide n! by the product of k! and (n-k)!
例题解析
输入
C(5,2)
结果
10
5! / (2! × 3!) = 120 / 12 = 10
常见错误注意事项
- ✕Confusing combinations with permutations
- ✕Incorrect factorial calculations
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