Arithmetic & Basics
Basic

Proportion (Cross Multiply)

Two equal ratios; solve using cross multiplication.

Formula

ab=cd⇒ad=bc\frac{a}{b} = \frac{c}{d} \Rightarrow ad = bc

Variables

a,b,c,dTerms of the proportion

Example

If 2/3 = x/9 then x = 6

Did You Know?

Cross-multiplication lets you solve for an unknown in a proportion — the basis of scaling recipes, maps, and models.

proportionratiocross multiplybasics