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

Step by Step Explanation:
  1. 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.
  2. 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
  3. 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.

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