alleryTwelve people each shake hands with all the others. Order of the pair is:
ANot interrupted
BNot important
CNot invented
DNot inspected
Answer & Solution
Correct answer: B. Not important
1. A handshake between two people happens once, not twice.
2. Counting it both ways round would double the answer.
3. Twelve persons meet in a room and each shakes hand with all the others.
4. Since the order within a pair does not matter, this is a combination.
_Source: syllabus Mathematics, Ch 6 'Permutations and Combinations'_
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