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smclean23: Master | Next Rank: 500 Posts; Posts: 172; Joined: Mon Jun 23, 2008 12:00 pm; Thanked: 3 times; Followed by:1 members

Almost there but not quite yet.....ADVICE...

by smclean23 » Sat Jul 05, 2008 5:18 pm

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.

Answer is D... :roll:

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Source: Beat The GMAT — Data Sufficiency | Sat Jul 05, 2008 5:18 pm

Vignesh.4384: Master | Next Rank: 500 Posts; Posts: 443; Joined: Sat Jun 28, 2008 6:33 pm; Thanked: 5 times

by Vignesh.4384 » Sat Jul 05, 2008 7:12 pm

I guess this is a simple problem if u read it carefully.

Since initially the table top is a square let it have a side if a.

initial area = a * a.

now the dimentions are altered and it is no longer a square.
so take L = a - 1
B = a + 2

u can even take it the other way.
B = a - 1 and L = a + 2. that wont be a problem

From option A :

L * B = 70

Above we have L and B in terms of a. so

(a-1) * (a+2) = 70

solve for a.
You wil get the initial surface area by using the formla
initial area = a * a.

From option B:

This option says there is a 25 % increase in one of the dimentions.

the questions says only one dimention increases (a + 2) while the other decreases.

so of the increase is 25 % then:

(125/100) * a = 2.

From this a can be found out.
To find out initial area use the formula.

initial area = a * a.