The scatterplot above shows the diameter x, in inches, and the age y, in years, of more than 40 trees in a certain park. Which of the following best describes the trend line of the scatterplot?

A) 2x+20
B) 5x+20
C) 10x+20
D) y=4x
E) y=12x

I got this one right, but it was really just a lucky guess. Scatterplots make no sense to me.

For this one, I think it’s more useful to think about the slope than it is to try to figure out the y-intercept. And to think about the slope, you need to pay attention to the scales on the x– and y– axes. I think a line that does a pretty decent job of approximating the trend can be drawn from the farthest left and farthest right points: about (1, 30) and (27, 150). What is the slope of that line?

\dfrac{150-30}{27-1}=\dfrac{120}{26}\approx 4.6

That rounds to about 5, which makes choice B look pretty good.

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