PSAT Math Multiple-Choice Question 295: Answer and Explanation

Question: 295

x	y
1
3	3
5
7

Which of the following equations relates y to x according to the values in the table above?

• A.
• B.
• C.
• D.

Correct Answer: A

Explanation:

A

Difficulty: Medium

Category: Linear Graphs

Strategic Advice: The answer choices are split into two types. The first two are linear equations and the second two are nonlinear. They are quadratic and exponential, respectively. Thus, examine the table to determine whether the relationship between x and y is linear or nonlinear.

Getting to the Answer: Notice that for every increase of 2 in x, y increases by . Thus, the relationship is linear, meaning you can eliminate (C) and (D). To determine whether (A) or (B) is correct, substitution could be used. However, note that if y increases by for every 2 unit increase in x, then dividing both values by 2 shows that y increases by for every 1 unit increase in x. This is the definition of slope, and the only equation that is a line with a slope of is (A).