Given 7 flags of different colors, how many different signals can be generated, if a signal requires the use of 3 flags one below the other?
Answer:
210
- There will be as many signals as there are ways of filling in 3 vacant places in succession by the 7 flags of different colors.
To find that we will use the fundamental principle of counting, which states,
“If an event can occur in m different ways, following which another event can occur in n different ways, then the total number of occurrence of the events in the given order is m \times n.” - The upper vacant place can be filled in 7 different ways by any one of the 7 flags.
The second vacant place can be filled in 6 different ways by any one of the remaining 6 different flags and so on.
Vacant Places Ways to fill 7 6 5 - Therefore, by the fundamental principle of counting, the number of different signals = 7 \times 6 \times 5 = 210.
Hence, the required number of different signals is 210.