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With 4 flags of different colours, signals using 2 flags one below the other number:
A18
B16
C14
D12
Answer & Solution
Correct answer: D. 12
1. The upper place has 4 choices.
2. The lower place then has 3.
3. That gives 12 signals.
_Source: NCERT Class 11 Mathematics, Chapter 7, Permutations and Combinations._
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