PSAT Math Multiple-Choice Question 651: Answer and Explanation

Question: 651

For every 8 units of x, there are consistently 12 units of y. If the relationship between x and y is given as an equation of the form y = kx , where k is a constant, what is the value of k ?

• A.
• B.
• C.
• D. 4

Correct Answer: C

Explanation:

(C) When x = 8, y = 12. We want to know the proportionality constant. We can do this by plugging the values of x and y into the equation and solving for k:

12 = 8k

Dividing by 8 tells us that . Reducing this fraction gives choice (C) as the answer, .