Question

In how many ways can 4 red, 3 yellow and 2 green discs be arranged in a row if the discs of the same colour are indistinguishable?

Answer 1

4 red, 3 yellow and 2 green discs.

Total discs = 9

Required number of ways

= $\frac{9!}{4!3!2!}$

= $\frac{9\times 8\times 7\times 6\times 5}{3\times 2\times 2}$

= 1260

Required number of ways = 1260