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?

Explanation

Total number of discs are `4+3+2=9`. Out of 9 discs, 4 are of the first kind (red), 3 are of the second kind (yellow) and 2 are of the third kind (green) -

Therefore, the number of arrangements `=9 !/4 ! 3 ! 2 !=1260`. . "