Question

permutation and combination solve question no.1

Answer 1

nP4=12 × nP2

np4/nP2=12

n!/(n-4)!/n!/(n-2)!=12

Now
(n-2)!/(n-4)!=12

(n-2)!/(n-4)(n-3)(n-2)!=12
Here (n-2)! Cancel

12(n-4)(n-3)=0
Ie (n-4)(n-3)=0

So n=4,3 ans