Your heart rate rises when you exercise.
during aerobic exercise, your heart rate
should be at least 0.7(220 - a), but no
more than 0.85(220 - a), where a is your
age. find the target range if you are 14
years old.

ANSWER:  

While doing the aerobic exercise, heart rate must be in the range of 144.2 bpm to 175.1 bpm for a 14 years old person.

SOLUTION:

Given, your heart rate rises when you exercise.  

During aerobic exercise, your heart rate should be at least 0.7(220 - a), but no more than 0.85(220 - a), where “a” is your age.  

We need to find the target range if you are 14 years old.

Here a = 14

For 14 years old, lower range is

0.7(220 – 14)

0.7(206)

144.2

Now, for 14 years old, upper range is

0.85(220 – 14)

0.85(206)

175.1

Hence, while doing the aerobic exercise, heart rate must be in the range of 144.2 bpm to 175.1 bpm for a 14 years old person.

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step-by-step explanation: