Questions
Every body in a room shakes hands with every body else. The total number of hand shakes is 66. The total number of persons in the room is
detailed solution
Correct option is B
Let total number of persons be n.Since two persons shake hands, so number of ways of shaking hands =nC2.According to question, we have nC2=66or n!(n−2)!2!=66 or n(n−1)(n−2)!(n−2)!2×1=66or n2−n=132 or n2−n−132=0or n2−12n+11n−132=0or n(n−12)+11(n−12)=0⇒n=−11 or 12But, n = –11 is not possible.∴ n=12.Similar Questions
If then equal to
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