Example 4 - Find number of different signals at least 2 flags - Fundamental principal of counting

  1. Chapter 7 Class 11 Permutations and Combinations
  2. Serial order wise
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Example 4 Find the number of different signals that can be generated by arranging at least 2 flags in order (one below the other) on a vertical staff, if five different flags are available? A signal can have at least 2 flags i.e. flag can have 2 flags or 3 flags or 4 flags or 5 flags We need to calculate separately for each and then add For 2 flags The required number of signals = 5 × 4 = 20 For 3 flags The required number of signals = 5 × 4 × 3 = 60 For 4 flags The required number of signals = 5 × 4 × 3 × 2 = 120 For 5 flags The required number of signals = 5 × 4 × 3 × 2 × 1 = 120 ways Hence, required number of signals = 320.

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