Permutations and Combinations
Given flags of different colours, how many different signals can be generated if each signal requires the use of flags, one below the other?
Solution: Since, each signal requires the use of flags.
There will be as many signals as there are ways of filling in vacant place in succession by the given flags of different colours.
The upper vacant place can be filled in different ways by any one of the flags .
The lower vacant place can be filled in different ways by any one of the remaining different flags.
Thus, by multiplication principle, the number of different signals that can be generated is