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. If the desirable heart rate for a man is 135 beats per minute, how old is he?
a.22.5 years old
b.40 years old
c.45 years old
d.42.5 years old
we are given with two equations: R=143-0.65a for women and R = 165-0.75a for men. In this prblem we are asked the age of a man when R is equal to 135. In this case, we use the second equation and substitute R with 135. In this case, 135 = 165 - 0.75 a; a is equal then to 40 yrs old. In 2, when x is equal to 4, then 0.5*4 + 3 is equal to 5.
