5 min read
2026-03-09
Proportions are one of the most practical parts of math. We use them every day, often without thinking about it.
Scaling a recipe to another number of servings is a classic proportion. If you need 300 g of rice for 6 servings, for 4 servings: 300 × 4 / 6 = 200 g.
On a 1:100 000 map, one centimeter on the map equals one kilometer in reality. Proportions convert between map distances and real distances.
Discounts: an item at 5000 with 15% off → 5000 × 85/100 = 4250
Figuring out interest on a loan
Splitting a budget across categories
Paint, wallpaper, or tile for a room: if 1 liter covers 8 m², you need 3 liters for 24 m².
Scaling images while keeping aspect ratio. If the original is 1920×1080, halving the width to 960 gives height 540.
Children’s drug doses are often proportional to body weight. Solution concentrations are also set with proportions.
Fuel use per 100 km lets you estimate fuel needed for any trip length.
See also: Fraction Calculator, Statistics, Equation Solver