Why does tennis count 15, 30, 40 instead of the usual 1, 2, 3 in scoring?

Answer 1

The scoring system in tennis uses 15, 30, 40 instead of 1, 2, 3 because it originated from a clock face. The hand on the clock would move from 15 to 30 to 45 (which was later changed to 40) to keep track of the score during a game.