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Permutation and Combinations — MATHS STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceMATHSPermutation and Combinations2 Marks
Question
If nC9 = nC8, find nC17
✓

Answer

We have, nC9 = nC8 
i.e., $\frac{n !}{9 !(n-9) !}=\frac{n !}{(n-8) ! 8 !}$
or $\frac{1}{9}=\frac{1}{n-8} $ or n - 8 = 9 or n = 17
Thus, nC17 = 17C17 = 1

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