Real World Applications – Algebra I
How can we represent a kid’s growing height as a linear relationship?
Let’s say a kid at 2 years old is 3 feet tall, or 36 inches. Using the information given, this kid will be 38.5 inches tall when 3 years old. Let’s write an equation representing this relationship using these two data points.
Given the information about the heights, we’d first have to calculate the slope (even though that was given to us). The slope would be,
Now let’s use one of our data points and the slope to find the equation to represent this relationship. We’re going to use the slope-intercept form to substitute what we know so far.
This means that at 5 years old, the child will be 38.5 inches tall.
Try asking a family member how tall you were at two different ages in your life, and practice finding the rate of change, or the slope between these two points. Would this equation make sense? Why or why not? Would this equation apply when you’re over 30 years old? Would you be getting taller at that age?