Question

20Pr = 6840
r = ?
permutations ka question h ye​

Answer 1

Answer:

We have,20Pr=6840⇒20!(20−r)!=20×342⇒20!(20−r)!=20×19×18×17!17!⇒20!(20−r)!=20!17!⇒(20−r)!=17!⇒r=3