Answer
$-40$
Work Step by Step
We first multiply the separate square roots together to create one square root. Then, we simplify $\sqrt{16}$ because it is a perfect square:
$-5\sqrt 8 \times 2\sqrt 2$
=$(-5\times2)\times(\sqrt 8\times\sqrt 2)$
=$(-10)\times(\sqrt {8\times2})$
=$(-10)\times(\sqrt {16})$
=$(-10)\times(\sqrt {4^{2}})$
=$(-10)\times(4)$
=$-40$
