Ballparking: Overview
The cornfields of Moses, each of which is 27 acres, have been damaged by the rootworm pest. A total of $$\frac{3}{11}$$ of Cornfield A has been destroyed, while $$\frac{8}{25}$$ of the crop in Cornfields B and C was lost. Cornfield D has been totally ruined and only $$\frac{1}{9}$$ of cornfield E was left undamaged. Finally, $$\frac{1}{6}$$ and $$\frac{1}{7}$$ of cornfields F and G were damaged, respectively. Which of the following is the closest approximation for the number of unharmed acres in Moses' cornfields?
Incorrect.
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Incorrect.
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Correct.
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* Cornfield A: $$\frac{8}{11}$$ unharmed
* Cornfield B: $$\frac{17}{25}$$ unharmed
* Cornfield C: $$\frac{17}{25}$$ unharmed
* Cornfield D: Totally destroyed
* Cornfield E: $$\frac{1}{9}$$ unharmed
* Cornfield F: $$\frac{5}{6}$$ unharmed
* Cornfield G: $$\frac{6}{7}$$ unharmed
Don't fall into GMAC's trap by doing all the dirty work; Trying to add up all these fractions will require a common denominator, precious time, precious time, and even more precious time. Instead, use Ballparking:
* $$\frac{5}{6}$$ and $$\frac{6}{7}$$, added to the $$\frac{1}{9}$$ to slightly round things, are nearly 2.
* $$\frac{17}{25}$$ is approximately $$\frac{2}{3}$$. Two times $$\frac{2}{3}$$ is "one and one-third", or 1.3.
* $$\frac{8}{11}$$ is "slightly over $$\frac{8}{12} = \frac{2}{3}$$", or about 0.7.
So the answer should be in the ballpark of
>$$2+1.3+0.7=4.0$$
actually, slightly less than that, as $$\frac{5}{6}+\frac{6}{7}+\frac{1}{9}$$ is less than 2. Multiply by 27 to get the total number of unharmed acres of corn. Ballpark again to save time; $$4 \times 27=108$$.
POE for something smaller than 108. The correct answer is C.
Incorrect.
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Incorrect.
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57
84
105
118
126
