Counting unique handshakes among friends
Riddle:
If 7 people meet and each shakes hands once with every other person, how many handshakes occur?
Answer:
Answer: 21. Explanation: Each handshake involves 2 people. We calculate the number of unique pairs of 7 people: combinations of 7 taken 2 at a time = 7×6/2 = 21 handshakes.