Find n, if: (15-n)!(13-n)! = 12 - Mathematics and Statistics

Sum

Find n, if: `((15 - "n")!)/((13 - "n")!)` = 12

`((15 - "n")!)/((13 - "n")!)` = 12

∴ `((15 - "n")(14 - "n")(13 - "n")!)/((13 - "n")!)` = 12

∴ (15 – n) (14 – n) = 4 × 3
Comparing on both sides, we get
15 − n = 4
∴ n = 11

Concept: Concept of Factorial Function

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Chapter 6: Permutations and Combinations - Exercise 6.2 [Page 76]

Chapter 6 Permutations and Combinations
Exercise 6.2 | Q 9. (ii) | Page 76

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