Q. 84.2( 5 Votes )

# If (n + 1)! = 90 [(n – 1)!], find n.

Answer :

Given: (n + 1)! = 90 [(n – 1)!]

To Find : n ?

⇒ (n + 1) × (n) × (n-1)! = 60 [(n – 1)!]

⇒ (n + 1) × (n) = 90

⇒ (n + 1) × (n) = 10 × 9

n = 9

Hence, n = 9

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Which of the following are true :

(2 + 3)! = 2! + 3!

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