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1. At the end of a banquet 10 people shake hands with each other . How many handshakes will be in total?
- A. 100
- B. 100
- C. 100
- D. 100
Answer: Option C
Explanation:
Everybody does 9 handshakes - but then they are counted twice, so 10 * 9 /2 = 45.
Alternative calculation:
Person no 1 does 9 handshakes
Person no 2 does 8 - he already has shaken hands with no1
And so on …
person no 9 does 1 handshake with person no 10
Btw person no10 has already shaken everybody’s hand, ok
So we get 9 + 8 + … + 1
The seven years old Gauß might tell you that this is 10 * 9 / 2 = 45
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