Data Sufficiency

AAPL wrote: ↑

Mon Mar 30, 2020 9:52 am

Professor Vasquez gave a quiz to two classes. Was the range of scores fro the first class equal to the range of scores for the second class?

1) In each class, the number of students taking the quiz was 26, and the lowest score in each class was 70.
2) In each class, the average (arithmetic mean) score on the quiz was 85.

The OA is E

Source: GMAT Prep

Target question: Was the range of scores for the first class equal to the range of scores for the second class?

Neither statement alone seems sufficient, so let's jump straight to....

Statements 1 and 2 combined
There are several scenarios that satisfy BOTH statements. Here are two:
Case a:
First class scores: {70, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 100}
Second class scores: {70, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 100}
In this case, the range for the first class EQUALS the range for the second class

Case b:
First class scores: {70, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 100}
Second class scores: {70, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 85, 86, 99}
In this case, the range for the first class is GREATER THAN the range for the second class

Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Aside: notice that for case b, I took the last two values (85 and 100) in the first class and replaced them with 86 and 99 for the second class. Since both pairs of numbers have the same sum, this ensured that the class average remained 85.

Answer: E

Cheers,
Brent