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Surface Area

by karthikpandian19 » Tue Dec 13, 2011 12:49 am
The surface area of a square tabletop was changed so that one of the dimensions was reduced by 1 inch and the other dimension was increased by 2 inches. What was the surface area before these changes were made?
(1) After the changes were made, the surface area was 70 square inches.
(2) There was a 25 percent increase in one of the dimensions.
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Source: — Data Sufficiency |

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by Anurag@Gurome » Tue Dec 13, 2011 12:59 am
karthikpandian19 wrote:The surface area of a square tabletop was changed so that one of the dimensions was reduced by 1 inch and the other dimension was increased by 2 inches. What was the surface area before these changes were made?
(1) After the changes were made, the surface area was 70 square inches.
(2) There was a 25 percent increase in one of the dimensions.
Let the side of square = x

(1) (x - 1)(x + 2) = 70
x² + x - 72 = 0
(x + 9)(x - 8) = 0
x = 8; SUFFICIENT

(2) x + 25% of x = x + 2
1.25x = x + 2
x = 8; SUFFICIENT.

The correct answer is D.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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