Forgetting magnitude C 1 2 3 4 5 6 7 8 9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 D 1 2 3 4 5 6 7 8 9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 a working slide rule