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Proportions Solutions

• A proportion is two    ratios    set equal to one another.

• When a proportion contains an unknown value, it can be determined by finding the    cross-product   .

  • This means to    multiply    the numerator of one ratio in the proportion by the denominator of the other ratio.


$ay=bx$


• • This results in an equation that you can use to solve for the    unknown value   .  

Example 1

Solve.

$\frac{x}{3}=\frac{7}{15}$

Implement	Explain
$15x=3\left(7\right)$
$\frac{15x}{15}=\frac{21}{15}$	Find the cross product
$x=\frac{21}{15}=\frac{7}{5}$	Solve for x

Example 2

Solve.  

$\frac{9}{4x}=\frac{8}{3}$

$\begin{array}{rcl}9\left(3\right)& =& 4x\left(8\right)\\ \frac{27}{32}& =& \frac{32x}{32}\\ x& =& \frac{27}{32}\end{array}$