36 people {a1, a2, ..., a36} meet and shake hands in a circular fashion. In other words, there are totally 36 handshakes involving the pairs, {a1, a2}, {a2, a3}, ..., {a35, a36}, {a36, a1}. Then size of the smallest set of people such that the rest have shaken hands with at least one person in the set is
" 11
" 18
" 12
" 13

• smallest set where shaken hand with at least one person
  a1 shaken hand with a36 and a2.similarly a4 shaken hand with a3 and a5.....and so on.
  in this way we get a series like
  a1 a4 a7 .....a34(this is nothing but the A P series)
  where
  tn=34
  a=1
  d=3
  tn=a+(n-1)d
  34=1+(n-1)3
  33=(n-1)3
  n-1=11
  n=12
  
  
• 11 years agoHelpfull: Yes(42) No(2)
• 12;
  12*2+12 =36
• 13 years agoHelpfull: Yes(10) No(22)
• SWETA VARDHAN
  why we are considering a1 and a4.. why not a2 or a3?
• 9 years agoHelpfull: Yes(4) No(2)