# What is cross multiplication?

Oct 26, 2014

We multiply the numerator of each (or one) side by the denominator of the other side.

For example, if I have want to solve for $x$ for the following equation:

$\frac{x}{5} = \frac{3}{4}$

I can use cross-multiplication, and the equation becomes:

$x \cdot 4 = 3 \cdot 5$

$4 x = 15$

$x = \frac{15}{4} = 3.75$