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13 May 2013, 10:53
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
70% (02:26) correct
30%
(02:38)
wrong
based on 311
sessions
History
Date
Time
Result
Not Attempted Yet
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?
(A) 20
(B) 24
(C) 28
(D) 32
(E) 36
Attachment:
square with area 84.JPG [ 22.64 KiB | Viewed 8753 times ]
Give yourself a strict time limit of 90 second for this question.
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:
https://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?
Mike
13 May 2013, 11:07
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We can solve this in 30 sec if we traspose the figures(refer to the image)
The area covered is \(\frac{2}{7}\) of the total (2 columns)
So area is \(84*\frac{2}{7}=24\)
The area covered is \(\frac{2}{7}\) of the total (2 columns)
So area is \(84*\frac{2}{7}=24\)
Attachments
square with area 84.JPG [ 33.21 KiB | Viewed 8529 times ]
General Discussion
13 May 2013, 11:02
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there are 7X7 squares. Area of each square is 84/49.
Now count the no of squares in yellow. If you face a triangle, try analysing it as a half of rectangle (2square). The total no of squares will be 24.
24 * 84/49 = 24.
IMO B.
Took me 01:59.
Any simpler approach?
Now count the no of squares in yellow. If you face a triangle, try analysing it as a half of rectangle (2square). The total no of squares will be 24.
24 * 84/49 = 24.
IMO B.
Took me 01:59.
Any simpler approach?
