## Elementary Algebra

$4 \sqrt{15}$
Recall, $\sqrt{a}\times \sqrt{b}= \sqrt{a \times b}$. Thus, we can multiply 20 and 12 to obtain the simplified expression: $\sqrt{20 \times 12}=\sqrt{240}$ In order to simplify a radical, we consider the factors of the number inside of the radical. If any of these factors are perfect squares, meaning that their square root is a whole number, then we can simplify the radical. We know that 15 and 16 are factors of 240. We know that 16 is a perfect square, so we simplify: $\sqrt{16} \sqrt{15}=4 \sqrt{15}$