Answer Choices
The amount of plastic, in billions of pounds, produced in the United States during the year 1985
The number of years it took the United States to produce 1 billion pounds of plastic
The average annual plastic production, in billions of pounds, in the United States from 1985 to 2003
The average annual increase, in billions of pounds, of plastic produced per year in the United States from 1985 to 2003
Explanation for Question 21 From the Math (Calc) Section on the Official Sat Practice Test 8
So question 21 gives us a graph and it also gives us the equation 2 that goes with the graph. And in the question we're asked, 3 what does the value of 3.39 mean? 4 We look in on this equation, we can see that 3.39 is the slope, 5 right? So 3.39 is the slope and slope is 6 rise over run, 7 right? So we can put it over one here to show the, 8 the run here and rise refers to the Y axis and run refers to 9 the X axis, right? So we're looking at a change here. 10 We're looking as something happens to our number of years, 11 something is going to happen to our amount of plastic. 12 And so we can see that a says the amount of plastic produced during 13 the year 1985. So that's not going to be our 3.39. 14 That would actually be our Y intercept, right? 15 Cause 1985 is happening at our y-intercept. 16 So a refers to the Y intercept here, not the slope. 17 Now B says the number of years that took the United States to produce 1 billion 18 pounds. Now, remember, this is a rate, 19 right? We're talking about changing the years is changing the changing the pounds. 20 So it's not a set number of years. It's a rate of change. 21 So B is no good either. Now C says the average annual plastic production. 22 And so we don't necessarily know that the slope is the average annual, 23 uh, plastic production. We don't have anything that tells us that here. 24 So DS or C is no good. And then D finally the average annual 25 increase of plastic per year. 26 And so this makes sense, right? Because if we see that we're rising 3.39 27 every year, then we're increasing the plastic production by 3.39 every 28 year. Right? So this is our increase in production of plastic. 29 And our one is the year that passes. 30 So D is going to be our best answer.