Consider a 20 sided convex polygon K, with vertices A1, A2.....A20 in that order.Find the No. of ways in which three sides of K can be chosen so that every pair among them has at least two sides of K between them.(For example(A1A2,A4A5,
A11A12) is an admissible triplet while A!A@,A4A5,A19A20)is not)

• 520 ways are possible.
• 13 years agoHelpfull: Yes(0) No(1)