## Geometry: Common Core (15th Edition)

$7 \sqrt {2}$
First, we rewrite the problem in the form of a fraction: $28 \div \sqrt {8} = \frac{28}{\sqrt 8}$ Let's look at the denominator. We can rewrite $8$ as the product of a perfect square and another factor. $8$ can be rewritten as $4 • 2$: $\frac{28}{\sqrt {4 • 2}}$ Take the square root of $4$: $\frac{28}{2 \sqrt {2}}$ Divide both the numerator and the denominator by their greatest common factor, $2$: $\frac{14}{\sqrt {2}}$ We do not like to leave radicals in the denominator. To get rid of the radical in the denominator, we multiply both the numerator and denominator by $\sqrt {2}$: $\frac{14 \sqrt {2}}{2}$ Divide the numerator and denominator by their greatest common factor, $2$: $7 \sqrt {2}$