[Video] Q8: The graph shows the average heart rate for 15 people before, during, and after a period of strenuous exercise. the horizontal axis shows time, in minutes, and the vertical axis shows average heart rate, in beats per minute. the exercise period began at 5 minutes and ended at 15 minutes. approximately how many minutes did it take after the exercise period ended for the average heart rate to first return to the average heart rate before the exercise period began?

Explanation for Question 8 From the Math (Calc) Section on the 2020 October Sat

So question eight gives us a graph that shows heart rate over time. 2 And they tell us in the question that at about five minutes, 3 people start doing strenuous activity. And then at about 15 minutes, 4 the strenuous activity stops. And the question is asking us how long after 5 the strenuous activity is done, does it take for the heart rate to return 6 to normal? And so what we want to do here is looking on this 7 graph and we see that right here is when our physical activity ended at 8 minute 15, and this is right about normal, 9 right, right. Under 80. So we get back to normal close here, 10 maybe around 24 to 23. 11 And so we need just, we just need to know the difference or the 12 difference between 15 and 24 to 23, 13 right? So 15 or 24 minus 15 gives us nine. 14 So we want to choose an answer choice that shows about nine to 10 15 ish minutes difference, and sure enough answer choice a shows nine. 16 And so all that means is that there was nine minutes between when their 17 exercise or when their workout ended, when their heart rate went back to normal.