## Thinking Mathematically (6th Edition)

To solve a proportion, use cross product principle which is stated below, Let $\frac{a}{b}::\frac{c}{d}$ are in proportion then, $a\times d=b\times c$. That is product of means = product of extremes. Example: If $2:x::\ 5:8$ then find the value of x $2:x::\ 5:8$ Product of means $=$ product of extremes $2\times 8=x\times 5$ This implies that, \begin{align} & x=\frac{2\times 8}{5} \\ & =\frac{16}{5} \end{align}