Question

Find 'n' if2ne, Me, =20:1

Answer 1

Answer:

P(n,4)=20×P(n,2)

⇒

(n−4)!

n!

=20×

(n−2)!

n!

⇒(n−2)!=20×(n−4)!

⇒(n−2)(n−3)=20

⇒(n−2)(n−3)=5×4

⇒n−3=4

⇒n=7