The recommended heart rate for weight management exercise and improving cardio fitness, in beats per minute, depends on a person's age and can be represented by the expression 0.7 (220-a) what is the recommended heart rate for a 20 year old person?

As per the question, the recommended heart rate (beats per minute) can be represented by the expression 0.7 (220-a), i. e. 0.7 * (220-a), where a is the age of the person.

We have to determine the recommended heart rate for a 20-year old person.

Substituting the value 20 for a in the expression

⇒ Recommended heart rate = 0.7 * (220 - 20)

⇒ Recommended heart rate = 0.7 * (200)

⇒ Recommended heart rate = 140 beats per minute

Recommended heart rate of a person of age 20 years will be 140 beats per minute.

Step-by-step explanation:

Expression representing the heart rate in terms of beats per minute is = 0.7 (220 - a) where a = age of the person.

Now we have to calculate the recommended heart rate for a person having age = 20 years.

Now we put a = 20 in the expression

Heart rate = 0.7 (220 - 20)

= 0.7 * (200)

= 140 beats per minute

Therefore, recommended heart rate of a person of age 20 years will be 140 beats per minute.