Question

If `""^("n" - 1)"P"_4 : ""^"n""P"_5` = 1 : 6, then n = ______.

विकल्प

• 6

• `1/6`

• 12

• `1/12`

Answer 1

If `""^("n" - 1)"P"_4 : ""^"n""P"_5` = 1 : 6, then n = 6.

Explanation:

`""^("n" - 1)"P"_4 : ""^"n""P"_5` = 1 : 6

∴ `1/6 = (""^("n" - 1)"P"_4)/(""^"n""P"_5)`

= `(("n" - 1)!)/("n"!)`

= `(("n" - 1)!)/("n"("n" - 1)!)`

⇒ n = 6