ayas7 wrote:
PerfectScores wrote:
oss198 wrote:
Attachment:
Picture 1.png
In the figure shown above, line segment QR has length 12, and rectangle MPQT is a square. If the area of rectangular region MPRS is 540, what is the area of rectangular region TQRS?
(A) 144
(B) 216
(C) 324
(D) 360
(E) 396
A very good contender for back solving, lets start with option C (Always start with C)
Area of rectangle.........Side QT.......Area of square.....Total area of the figure
(A) 144
(B) 216
(C) 324....................324/12=27.... 27*27 =729........... 729 + 324 = 1053
(D) 360
(E) 396
The total area was supposed to be 540 however it is 1053 hence we move up (go for smaller values). Now we know that answer is either A or B so we try any of them.
Area of rectangle.........Side QT.......Area of square.....Total area of the figure
(A) 144
(B) 216....................216/12 =18.....18*18 =324.......... 324 + 216 =540 (BINGO!)
(C) 324....................324/12=27.... 27*27 =729........... 729 + 324 = 1053
(D) 360
(E) 396
Answer is B.
why do you always start with C? Also can you please explain your strategy? Thanks.
ayas7 , a comment and links that might help.
For questions where the answer choices are listed in ascending order, and we want to backsolve, we start with C because it is the middle value. C gives a benchmark.
If C yields an answer that is too large? Toss out Answers D and E, which will be greater than C. Then we only have to pick between Answers A and B.
There are two really good explanations for starting with C, given by a GMATclub expert,
HEREand
HERETHIS POSTby
Bunuel includes the link I gave above, and a lot more. Scroll down slightly to "2. Strategies and Tactics."
One more. The post immediately above, which I just found rather accidentally, is part of what looks to be a phenomenal collection, Ultimate GMAT Quantitative Megathread, by
Bunuel, composed of GMAT Quant . . . everything.
MEGATHREAD HERE Hope that helps.
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