Question

Medical researchers have determined that for exercise to be beneficial, a personâ€™s desirable heart rate, r, in beats per minute, can be approximated by the formulas r = 143 minus 0.65 a for women r = 165 minus 0.75 a for men, where a represents the personâ€™s age. if the desirable heart rate for a woman is 130 beats per minute, how old is she? a. 84 years old b. 57 years old c. 37 years old d. 20 years old

1. thnahdat
She is 20 years old when her heart rate is 130 beats per minute.

### What are Linear Equation?

Linear equation are those in which power is 1 or maximum degree is 1. For example: x + y = 3 here the maximum degree is 1.
Linear equation can be in:
One variable, Two variable and might be N- number of variable.
Here, We have given Two Linear equations:
1. For Men: r = 165 – 0.75(a)
2. For Women: r = 143 – 0.65(a)
where ‘a’ represents the person’s age.
Now, Here we have given Women’s heart rate, r = 130 beats per minute.
using second equation,
r = 143 – 0.65(a)
130 = 143 – 0.65(a)
0.65(a) = 143 – 130
0.65 (a) = 13
a = 13/0.65
a = 20 years
Hence,
She is 20 years old when her heart rate is 130 beats per minute.