If

*a*,*b*and*c*are numbers connected by the proportion \(\dfrac{a}{b}\) = \(\dfrac{b}{c}\), then*c*= \(\dfrac{b^{2}}{a}\) and*c*is called the third proportional.In a proportion with three terms that are, in order,

*a*,*b*and*c*, the third proportional is*c*.### Examples

- In the proportion \(\dfrac{x}{12}\) = \(\dfrac{12}{16}\), 9 is the third proportional, because
*x*= 9. - In the proportion \(\dfrac{12}{18}\) = \(\dfrac{18}{x}\), 27 is the third proportional, because
*x*= 27.