Question

Find the third proportional to $12,18.$

Answer 1

Let the third proportion be $x$

$12:18=18:x$

$\Rightarrow \frac{12}{18}=\frac{18}{x}$

$\Rightarrow x=18\times \left(\frac{18}{12}\right)$

$\Rightarrow x=18\times \left(\frac{3}{2}\right)$

$\Rightarrow x=\frac{54}{2}$

$\therefore x=27$

Hence, the third proportional to $12,18$ is $27.$