Three crates of stones, one of them is off. Use the balance scale to find it in as few weighings as you can.
Crate 1 / 3Weighings 0 / 4Score 0
Rules: stones are numbered from 1. Put some stones in the left pan and the same number in the right pan; the scale says LEFT heavy, RIGHT heavy or BALANCED. Crate 1: 9 stones, one is heavier. Crate 2: 12 stones, one is either heavier or lighter (you must say which). Crate 3: 27 stones, one is heavier. Answering costs nothing but a wrong answer pays 0. A right answer pays 100 minus 20 for every weighing beyond the minimum (2, 3 and 3). Each crate allows the minimum plus 2 weighings. Max score 300.