A group of 13 friends were planning a trip. On night before they made lot of phone calls. Each friend talked to every other friend atleast once. what is fewest phone calls that can be made?

Answer 1

13 * 12 = ?

Answer 2

thank you Ms. Sue. But how did you arrive to 13*12? can you please explain - i did not understand

Answer 3

Each of the 13 friends called 12 other people.