Question

two trains leave the same city at the same time, one going east and the other going west. If one train is traveling at 65 miles per hour and the other at 72 miles per hour, how many hours will it take for them to be 822 miles apart

Answer 1

The effect of both trains moving in opposite directions is the same that if one of them was stationary and the other one was moving at 65 + 72 = 137 mph.

Now, we know that distance = speed x time. Let's call the distance d and the time y

We would have:

$d=137t$

Using the distance we're given,

$822=137t$

Solving for t :

$\begin{gathered} 822=137t \\ \rightarrow\frac{822}{137}=t \\ \Rightarrow t=6 \end{gathered}$

It would take 6 hours for them to be 822 miles apart .