Answer
$16$ hours
Work Step by Step
Since the time required to assemble computers varies DIRECTLY with the number of computers assembled and INVERSELY with the number of workers, we can express this in the following manner:
$$t=\frac{kc}{w}$$
where $t$ = time required to assemble computers, $c$ is the number of computers assembled, $w$ is the number of workers, and $k$ is a proportionality constant. Since we know that, when $c = 30$ and $w=6$, then $t=10$, we can calculate $k$:
$$t = \frac{kc}{w}$$
$$\frac{tw}{c} = k$$
$$\frac{(10)(6)}{30} = k = 2$$
and finally answer the question:
$$t = 2(\frac{40}{5}) = 16$$
