Probability — O/L Mathematics

Every day you weigh chances without noticing: will it rain before you reach home, which cricket team is likelier to win, is it worth buying one more lottery ticket. Probability is the branch of maths that turns "probably" and "unlikely" into exact numbers you can compute and compare. At O/L it is a reliable source of marks, and beyond school it underpins insurance, medicine, weather forecasting and quality control — anywhere people must plan sensibly under uncertainty.