9 balls

8 are same weight
1 is heavy

have balance that says if right/left is heavier

find heavy ball in two uses of scale




can reduce to 4 balls in 1 weighing:
4 vs 4 (vs 1)     if same weight then outer ball wins
if diff weight then down to 4

4 balls
22    => reduces to 1 remaining
11(2) => still possibly one remaining


3 vs 3 (3) => know which group of 3 has the ball
11 (1)   => know which is the ball


