Data Sufficiency

[GMAT math practice question]

78% of all students at a school enrolled in an English class and 79% enrolled in a Math class. What percent of the students enrolled in neither English nor Math classes?

1) 13% of students enrolled in a Math class only.
2) 12% of students enrolled in an English class only.

=>
Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question.

For questions related to 2x2 matrices and percentages, we need 3 values or percentages for sufficiency. Since the original condition gives us 2 percentages, we need 1 additional percentage to solve the problem.

Each condition gives us one percentage. Thus, each condition is sufficient.

Therefore, the answer is D.

Answer: D