Linear inequalities in two variables

Question

The graph on the right shows the solution set of the given system of inequalities, where H is the heart rate and A is the age, for the target heart rate of a particular exercise goal as a function of the age of the person exercising. Answer parts A and B.

10 ≤ a ≤ 70 Range of ages

H ≥ 0.7(220 - a) Minimum target rate

H ≤ 0.8(220 - a) Maximum target rate

a. What are the coordinates of point A and what does this mean in terms of age and heart rate?

Answer 1

H is at least .7(220-70) = .7(150) = 105

H is no more than .8(220-10) = .8(210)= 168

105<H< 168 when 10<A<70

(A,H)= (10,105) to (70,168)

A=Age in years

H= correspnding Heart rate, beats per minute

these numbers appear to be for safe running heart beats when exercising, for given age levels