Question

Find the number of permutations of n distinct things taken r together, in which 3 particular things must occur together.

Answer 1

Answer:.

$^{n-2}P_{r-2}\cdot 3!$ is the number of permutations.

Step-by-step explanation:

We have been given the number  of permutation of n distinct things taken r together, in which 3 particular things must occur together

Things occuring together is taken as 1.

That means r becomes r-2 and n=n-2.

$^{n-2}P_{r-2}\cdot 3!$

And $^nP_r=\frac{n!}{(n-r)!}$