Bunuel wrote:

Plane X flies at r miles per hour from A to B. Plane Y flies at S miles per hour from B to A. Both planes take off at the same time. Which plane flies at a faster rate? Town C is between A and B.

(1) C is closer to A than it is to B.

(2) Plane X flies over C before plane Y

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.

. <-- a --> <-- b -->

|---------|---------|

A--------C---------B

..| t1 | t2

-------------------------

v | r | 5

-------------------------

d | a | b

Question asks if r < 5 or r > 5.

Since we have 3 variables and 0 equation, E is most likely to be the answer.

If E is most likely to be the answer, we need to check both conditions 1) & 2) together first by VA method.

Condition 1) & 2)

We have conditions a < b and a/r < b/5 from 1) and 2).

a = 1, b = 2, r = 6 ==> r > 5

a = 20, b = 30, r = 4 ==> r < 5

The answer is E.

For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80 % chance that E is the answer, while C has 15% chance and A, B or D has 5% chance. Since E is most likely to be the answer using 1) and 2) together according to DS definition. Obviously there may be cases where the answer is A, B, C or D.

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