when Mario starts to jog, his heart rate increases by 10 beats per minute every 20 steps
If Mario's heart rate increases by 10 beats per minute every 20 steps, we can use this information to determine the rate of change of his heart rate.
The ratio of steps to heart rate change is 20 steps: 10 beats per minute.
To find the rate of change per step, we divide the change in heart rate (10 beats per minute) by the number of steps (20 steps).
Therefore, the rate of change per step is 10/20 = 1/2 beats per minute per step.