physics
posted by jer .
The speed of a nerve impulse in the human body is about 100 m/s. If you accidentally stub you toe in the dark, estimate the time it takes the nerve impulse to travel to your brain. (Assume that you are approximately 1.8 m tall and that the nerve impulse travels at uniform speed.)

d = V * t,
1.8 m = 100 m / s * t,
t = 1.8/100 = 0.018 s. 
0.18

general formula: V=distance/time
in this problem we are looking for the time, so adjusting our general formula we need to get time as our isolated variable.
time=distance/velocity
time: ?
distance: 1.8m
velocity: 100m/s
therefore: t=1.8m/100m/s
using your calculator you get:0.018s
the meters cancel out with each other as you are dividing. hope this helped, it can be confusing even for me.