Question

nPr = 210 find value of n​

Answer 1

Answer:

We have,

n

P

r

=5040 and

n

C

r

=210,

(n−r)!

n!

=5040 and

(n−r)!r!

n!

=210

Divide both

⇒r!=24⇒r=4

So

(n−4)!

n!

=5040

⇒

(n−4)!

n(n−1)(n−3)(n−4)!

=5040

⇒n(n−1)(n−2)(n−3)=5040

⇒n=10