Alan has embarked on an exercise program on his new treadmill. The graph at the right shows his heart rate during one of his daily 40 minute workouts.

1. Write a series of descriptive events (a "story") that can be represented by the changes in this graph.
Possible answer: Alan starts out with a slow 5 minute warm-up. He then steadily increases his speed in the next 5 minutes until he reaches a heart rate of 110 beats per minute. He maintains that rate for 20 minutes, after which he steadily cools down until he returns to his starting heart rate.

2. At what rate was Alan's heart rate decreasing during his cool down?
Answer: The cool down started at 110 beats per minute and ended with 70 beats per minute, over a period of 10 minutes.


(The negative sign indicates his heart rate is slowing down.)

Alan's heart rate was changing at a rate of -4 heart beats per minute during the cool down.
He was decreasing his heart rate by 4 beats per minute during the cool down.