Answer
$\frac{385}{324}\approx1.2$
Work Step by Step
Let d = distance between 55 and 35 mi/h signs = distance between 35 and 25 mi/h signs
First option:
$time=\frac{distance}{speed}$
$t_{A}=\frac{d}{55} + \frac{d}{35}=\frac{18d}{385}$
Second option:
$x=\frac{1}{2}(u+v)t$
$t=\frac{2x}{u+v}$
Between 55 and 35 mi/h signs:
$t=\frac{2d}{55+35}=\frac{d}{45}$
Between 35 and 25 mi/h signs:
$t=\frac{2d}{35+25}=\frac{d}{30}$
$t_{B}= \frac{d}{45} + \frac{d}{30} = \frac{d}{18}$
$t_{B}/t_{A}=(\frac{d}{18})/(\frac{18d}{385})=\frac{385}{324}\approx1.2$
