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S={1, 3, 5, 7,.............,397, 399}
Set S consists of the odd numbers from 1 to 399, inclusive. How many different ordered pairs $$(p, t)$$ can be formed, where $$p$$ and $$t$$ are numbers in S and $$p \lt t$$?
(Note: The sum of the integers from $$1$$ to $$n$$, inclusive, is given by the formula $$\frac{n(n+1)}{2}$$ for all positive integers $$n$$.)
Set S consists of the odd numbers from 1 to 399, inclusive. How many different ordered pairs $$(p, t)$$ can be formed, where $$p$$ and $$t$$ are numbers in S and $$p \lt t$$?
(Note: The sum of the integers from $$1$$ to $$n$$, inclusive, is given by the formula $$\frac{n(n+1)}{2}$$ for all positive integers $$n$$.)
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· 相关考点
6.3.5 组合
6.3.5 组合
以上解析由 考满分老师提供。
