On a unit test in a statistics class, the teacher determines that the mean test grade was 77.5 with a standard deviation of 5.2. What is the test grade, rounded to the nearest whole number, with a z-score of 2.4?

Use the z-score formula rearranged to find the grade: grade = mean + (z-score × standard deviation). Substituting the values gives 77.5 + (2.4 × 5.2) = 77.5 + 12.48 = 89.98, which rounds to 90. The correct choice is 90.

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