Ease Into Prep with an SAT^® Question of the Day

You are told that the function is exponential, which means that the y-values are not changing by a constant amount. You can immediately eliminate (A) and (B) because these describe linear functions (the value decreases by a constant amount each time). To choose between (C) and (D), think logically about how the graph would be labeled (if it had labels). The value of a car depends on how many miles it has been driven, so value would be plotted along the y-axis and miles driven would be plotted along the x-axis.

The exponential equations are in the form y = y₀(1+r)^x, where y₀ is the initial value and r is the rate of change. Thus, y₀ = 30,000, and 1 + r = 0.88 or r = −0.12. For every 5,000-mile increase, the value of the car decreases by approximately 12 percent. Choice (C) is correct.