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प्रश्न
Thirteen guests have participated in a dinner. The number of handshakes that happened in the dinner is:
विकल्प
715
78
286
13
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उत्तर
78
Explanation:
To handshakes, we need two guests.
Number of selecting 2 guests from 13 is 13C2 = `(13 xx 12)/(2 xx 1)` = 78
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