Question

Medical researchers have determined that for exercise to be beneficial, a person’s desirable heart rate, R, in beats per minute, can be approximated by the formulas

R=143-0.65a for women
R=165-0.75a for men,

where a represents the person’s age. What would the desirable heart rate be for a 46 year old woman?
a. 113 beats per minute
b. 172.9 beats per minute
c. 143.7 beats per minute
d. 63 beats per minute

Answer 1

I would say a) 113 beats per minute:
substituting 46 for a in the formula: R=143-0.65a you should get 113.

Answer 2

Option a is correct.

The desirable heart rate be for a 46 year old woman is, 113 beats per minute.

Explanation:

Here, R represents a person's desirable heart rate(in beats per minute)

and a represents the person's age.

The desirable heart rate of a person's can be approximated by the formulas;

For women:

`R = 143 - 0.65a` ......[1]

For men:

`R = 165- 0.75a` ......[2]

To find the desirable heart rate be for a 46 year old woman.

⇒
`a = 46 \text{years old woman}`

Substitute in [1] we get;

`R = 143 - 0.65(46)=143 -29.9 \approx 113` beats per minute

Therefore, 113 beats per minute would the desirable heart rate be for a 46 years old woman.