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Ratio & Proportion
· History📜 History & Discovery
The Egyptian Rhind Papyrus (~1650 BCE) used unit fractions and ratios in practical problems. Euclid's Elements Book V defined proportion rigorously without using numbers. Ancient architects used the golden ratio φ ≈ 1.618 in the Parthenon. Indian Vedic mathematics had rules for proportional reasoning (the "Rule of Three").
⚡ 2026 Update
The criss-cross "alligation" rule is used by every wholesale trader who blends teas, coffees, fuels or alloys. To mix two ingredients of cost a and b at mean price m, the ratio is (b − m) : (m − a). Bank PO and SSC papers test this almost every cycle.