Inverse Proportion — O/L Mathematics

When more workers join a job it finishes sooner; when a bus goes faster it arrives earlier. In each case one quantity grows while the other shrinks — but something hidden stays fixed. Inverse proportion is the maths that names that fixed thing and lets you predict the "how much" exactly: how many days, how fast, how many people. It shows up every year at O/L, in physics later (Boyle's Law), and in everyday planning.