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And we're getting mathy with it.

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The table below gives the average maximum heart rate, by age, for a person exercising at full effort.

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(Heart rate is in beats/min.)

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Find an algebraic equation to correspond with the data.

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Use a for age and h for heart rate.

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And here are your possible answers...

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Okay, if we look at the data…

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as age increases by 5, average max heart rate decreases by 5.

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Since age acts as our independent variable and average max heart rate acts as our dependent variable,

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we can calculate the change in average heart rate over age as the slope of our equation.

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Which gives us negative 1. That's the slope.

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The point slope form of a linear equation is y minus y1 equals slope times x minus x1.

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And you should get that there are 2 points we’re thinking through here…

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...that’s (x, y) and (x1, y1). h is y in this situation because it's the

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dependent variable, and a is x in this situation because it's the independent variable.

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We can take any x1 and y1 points... so let's just take the points 20 and 200.

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Plugging into the equation with these numbers then, we get... h - 200 = -1(a - 20).

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h minus 200 equals negative a plus 20.

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Adding 220 to both sides of the equation... we have h equals 220 minus a.

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Let's make sure this equation checks out with the data in the table....

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Let’s plug in age 45 and see if the end answer is right.

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Plugging in a equals 45...

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h = 220 - 45, so that's 175.

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Check it here on the table and yup, it checks out!

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So our equation is h equals 220 minus a.

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Answer A is our guy!

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