Answer
$\frac{1}{2}$
Work Step by Step
Given Information: When $d=$ distance, $r=$ rate of travel, and $t=$ time spent traveling, the distance formula is $d=rt$. $d=20$, $r=40$ miles per hour, and $t$ is unknown. If we substitute the known variables into the equation, it becomes:
$20=40t$
$t=20\div40=\frac{1}{2}$
In the context of the distance formula, this would mean that half an hour, or 30 minutes, was spent traveling. However, the question does not ask for the answer to be rephrased in the context of the situation, so $\frac{1}{2}$ should be sufficient.
