# How do you use cross products to solve 6.8/z=2/5?

Aug 2, 2017

$z = 17$

#### Explanation:

$\text{given an equation with 2 equal fractions then}$

•color(white)(x)a/b=c/drArraxxd=bxxc

$\Rightarrow \frac{\textcolor{b l u e}{6.8}}{\textcolor{red}{z}} = \frac{\textcolor{red}{2}}{\textcolor{b l u e}{5}} \leftarrow \text{cross-multiply}$

$\Rightarrow \textcolor{red}{z} \times \textcolor{red}{2} = \textcolor{b l u e}{6.8} \times \textcolor{b l u e}{5}$

$\Rightarrow 2 z = 34$

$\text{divide both sides by 2}$

$\frac{\cancel{2} z}{\cancel{2}} = \frac{34}{2}$

$\Rightarrow z = 17$

$\textcolor{b l u e}{\text{As a check}}$

$\text{left side "=6.8/17=0.4=2/5=" right side}$

$\Rightarrow z = 17 \text{ is the solution}$