70% of students at a school joined the soccer club and 60% j

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[GMAT math practice question]

70% of students at a school joined the soccer club and 60% joined the baseball club. What percent of students joined both clubs?

1) 10% of students joined neither of the clubs.
2) 20 students joined both clubs
Source: — Data Sufficiency |

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by Max@Math Revolution » Wed Jul 18, 2018 3:44 am

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=>

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.

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

As condition 1) gives information about a percentage, it is sufficient.

As condition 2) does not give information about a percentage, it is not sufficient.

Therefore, the answer is A.

Answer: A