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प्रश्न
Find n, if: `((15 - "n")!)/((13 - "n")!)` = 12
उत्तर
`((15 - "n")!)/((13 - "n")!)` = 12
∴ `((15 - "n")(14 - "n")(13 - "n")!)/((13 - "n")!)` = 12
∴ (15 – n)(14 – n) = 12 = 4 × 3
∴ (15 – n)(14 – n) = (15 – 11)(14 – 11)
∴ n = 11.
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