Give yourself a strict time limit of 90 second for this question
square with area 84.JPG [ 22.64 KiB | Viewed 484 times ]
The big outside purple square above has an area of 84, and the dots are all equal spaced, forming smaller squares. What is the sum of the areas of the shaded yellow regions?
GMAT students often say, "I could do better on the GMAT Quant if I had unlimited time, but I am always running of time on the hard problems, and I don't know how to do the math faster." Problems such as this, when done via a methodical, long, tedious calculation, can take quite some time, and open up the possibility of numerous calculation errors. When a problem like this appears on the GMAT, there simply has to be some insight method that presents a shortcut to the answer, much easier than the long tedious piece-by-piece calculation.
See this blog for a detailed discussion of this problem-solving perspective:http://magoosh.com/gmat/2013/how-to-do- ... th-faster/
as well as a complete solution to this particular question.
Experts: any tips you would like to add for doing GMAT math faster?
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