During exercise, the recommended maximum heart rate in beats per minute is modeled by the formula M=176-0.8A, where M is the maximum heart rate and A is the person’s age. Approximately, at what age would you have a recommended heart rate in beats per minute of 140

40 years
50 years
25 years
45 years

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To find the age at which the recommended heart rate is 140 beats per minute, we can first set up the formula:

M = 176 - 0.8A

Substitute M with 140:

140 = 176 - 0.8A

Rearrange the equation to solve for A by moving the constant term to the other side:

0.8A = 176 - 140

0.8A = 36

Divide both sides of the equation by 0.8 to solve for A:

A = 36 / 0.8

A ≈ 45

So, approximately at 45 years of age, the recommended heart rate during exercise would be 140 beats per minute. Therefore, the answer is 45 years.