Chapter 5 - Section 5.2 - More Work with Exponents and Scientific Notation - Exercise Set - Page 268: 82

$9.0\times10^{-3}$

Using laws of exponents, the given expression simplifies to \begin{align*} & \dfrac{0.00072\times0.003}{0.00024} \\\\&= \dfrac{7.2\times10^{-4}\times3.0\times10^{-3}}{2.4\times10^{-4}} \\\\&= (7.2\times3.0\div2.4)(10^{-4}\times10^{-3}\div10^{-4}) \\\\&= 9.0\times10^{-4+(-3)-(-4)} \\\\&= 9.0\times10^{-3} .\end{align*}