Question

Satish is making school spirit keychains, which consist of a sequence of n beads on a string. He has blue beads and gold beads. How many unique keychains can he make with exactly k ≤ n blue beads?

Answer 1

`(n!)/(k!(n-k)!)`

Explanation:

Satish is making school spirit key chains, which consist of a sequence of n beads, that are blue and golden.

Also given, there are k ≤ n blue beads.

So, the number of unique key chains that can be made is :

`(n!)/(k!(n-k)!)` ;
`k\leq n`