How many different signals can be transmitted by arranging 2 red, 3 yellow and 2 green flags on a pole, if all the seven flags are used to transmit a signal?
To find: Number of distinct signals possible
Total number of fags = 7
2 are of 1 kind, 3 are of another kind, and 2 are of the 3rd kind
number of distinct signals = 
Hence 210 different signals can be made
1