What is a ratio?

A ratio expresses the proportional relationship between two quantities. Written as A:B, it reads "A to B." For instance, a ratio of 12:8 simplifiés to 3:2 by dividing both terms by their greatest common divisor (4 in this case).

Practical examples

  • Cooking: a recipe calls for 3 cups of flour to 2 cups of sugar, giving à 3:2 ratio. Doubling yields 6:4, which simplifiés back to 3:2.
  • Mixing: standard concrete uses a cement/sand/gravel ratio of 1:2:3.
  • Scale: à 1:25,000 map means 1 cm on paper equals 250 m in reality.

The golden ratio

Perhaps the most famous ratio is the golden ratio (approximately 1:1.618), found in architecture, art, and nature. The Parthenon's proportions, the spiral of a nautilus shell, and the arrangement of sunflower seeds all follow this remarkable relationship.