Question

A train travels at a constant speed. What is the train's speed between checkpoints, expressed as a unit rate? Use the information given in the picture to help you.

Answer 1

Remember that the speed is the rate of change of the position with respect to time, so to solve this we are going to use the kinematic equation: $S= \frac{d_{f}-d_{i}}{t_{f}-t_{i}}$
where 
$S$ is the speed of the train
$d_{i}$ is the initial distance
$d_{f}$ is the final distance 
$t_{i}$ is the initial time 
$t_{f}$ is the final time 

Since checkpoint A is the initial checkpoint, we can infer that $d_{i}=105$ and $t_{i}=2$. Similarly, since checkpoint B is the final checkpoint, we can infer that $d_{f}=285$ and $t_{f}=5$. Lets replace the values in our kinematic euation:
$S= \frac{d_{f}-d_{i}}{t_{f}-t_{i}}$
$S= \frac{285-105}{5-2}$
$S= \frac{180}{3}$
$S=60$ mph

We can conclude that the train's speed between checkpoints is 60 mph.

Answer 2

The checkpoints is 60 mph if you have any questions just ask:)