Cross-multiplication - Rule of Three


In mathematics, specifically in elementary arithmetic and elementary algebra, given an equation between two fractions or rational expressions, one can cross-multiply to simplify the equation or determine the value of a variable.The Rule of Three was a shorthand version for a particular form of cross multiplication, often taught to students by rote.

Related formulas


a'extreme' of the proportion (dimensionless)
b'means' - same units as "x" (dimensionless)
c'means' - same units as "a" (dimensionless)
xrule of three (dimensionless)