Solution Step 0/0
At a secret meeting, everyone shakes hands exactly once with every other person present. Altogether there are 45 handshakes.
How many people attended the meeting?
How many people attended the meeting?
Explanations
10 people. Each shakes hands with nine others: each handshake is shared by two people.In the nine diagrams to the left, 10 dots represent the participants, the solid lines - the unique handshakes, the dotted lines - handshakes which have been already made from the preceding diagrams. Decreasing from 9 to 1 the sum of the unique handshakes through all nine diagrams is 45.
Check 10
Check 12
Check 13
Check 15
