Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
If Paula drove the distance from her home to her college at an average speed that was greater than 70 kilometers per hour, did it take her less than 3 hours to drive this distance?
(1) The distance that Paula drove from her home to her college was greater than 200 kilometers.
(2) The distance that Paula drove from her home to her college was less than 205 kilometers.
When it comes to inequality questions, it is important that if range of que includes range of con, that con is sufficient.
When you modify the original condition and the question, if Paula drove greater than 70 kilometers per hour, it would take less than 3 hours, which is less than 70km*3=210km. Then, you need to figure out the distance, which makes 1 variable and it should match with the number of equations. So you need 1 equation.
For 1), if the distance is farther than 200km, the range of que doesn’t include the range of con, which is not sufficient.
For 2), if the distance is less than 205km, the range of que includes the range of con, which is sufficient.
Therefore, the answer is B.
For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
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