PSAT Math Grid-Ins Question 139: Answer and Explanation

Question: 139

The variables m and n have a directly proportional relationship given by the equation m = kn, where k is a constant of proportionality. When m = 10, n = 2 . What will be the value of n if m equals 38?

Correct Answer: 7.6

Explanation:

7.6 Plug in the given values for m and n to determine what the value of the constant k is:

m = kn

10 = k × 2

5 = k

Now plug in 38 for m and 5 for k to get the value of n:

38 = 5n

7.6 = n