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Exercise 408Combinatorics › Binomial coefficientsHigh schoolAdded 3 Nov 2026

Simplifying binomial quotients

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Statement

Simplify (n+1k)(nk)\frac{\binom{n+1}{k}}{\binom{n}{k}}.

Hint

Use the factorial formula.

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Solution

Compute. (n+1k)(nk)=(n+1)!k!(n+1−k)!⋅k!(n−k)!n!=n+1n+1−k\frac{\binom{n+1}{k}}{\binom{n}{k}}=\frac{(n+1)!}{k!(n+1-k)!}\cdot\frac{k!(n-k)!}{n!}=\frac{n+1}{n+1-k}.

Conclusion. The quotient is n+1n+1−k\frac{n+1}{n+1-k}.