Many people think that the GRE is designed to test your math and verbal skills. While this is true to some degree, the tests are really designed to test your critical thinking skills. Trying to “math” your way through every problem on the quantitative section is possible, but it will likely take a lot of time. Let’s take a look at a sample GRE question and see how we can solve it in different ways.
On Monday, 2/5 of a full tank of water is emptied. On Tuesday, 1/5 of what’s left is emptied out of the tank. How full is the tank on Wednesday?
First, we’ll go through the math. Then we’ll talk about how to do this problem without math.
The tank is originally completed full, or 5/5 full. Then 2/5 of the tank is emptied, so 5/5 – 2/5 = 3/5. At the end of Monday, the tank is 3/5 full.
Then 1/5 of the remaining water is emptied. 1/5 of 3/5 means 1/5 x 3/5 = 3/25. So on Tuesday, 3/25 of the overall volume of the tank is drained. So 3/5 is left, then 3/25 is taken out, so we’ll need to convert the numbers into common denominators and we end up with 15/25 – 3/25 = 12/25. The tank remains 12/25 full.
There’s the math based way to solve this question. But because the GRE is actually a critical thinking test, is there another way to solve this problem what will get you to the answer more quickly?
Let’s take a look at how to do this without so much math
Take a look at the answer choices. On the first day, 2/5 of the tank is drained, leaving 3/5. No matter what, more water will be drained, so E cannot be the answer. Further, this problem is more complicated than simply doing this math: 1 – 2/5 – 1/5 = 2/5. Eliminate C.
If you simply multiply 1/5 and 2/5, you get 2/25, and we can eliminate A, as that is too easy. This leaves us with B] and D], and if you simply consider that the tank should still be around half full, after 1/5 of 3/5 is removed, only D] remains in the ballpark.
Approaching the problem in this way will save you time, if you know how to apply these methods. This is what preparing for the GRE is all about. Not just hammering at questions with direct math and being fast at it. It is about recognizing what the test is actually testing. The second method will take far less time on test day, and time management is a huge part of attaining a high score on the GRE.
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