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The top surface area of a square tabletop was changed so that one of t

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New post 19 Nov 2019, 10:33
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The top 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 change in one of the dimensions.


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The top surface area of a square tabletop was changed so that one of t  [#permalink]

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New post Updated on: 20 Nov 2019, 04:39
gmatbusters wrote:
The top 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 change in one of the dimensions.


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Answer A

S1:Let initial side of square=a
After changes,area=(a-1)*(a+2)=70
Now there is a difference of 3 between (a-1) & (a+2) and 70=7*10
So a-1=7=> a=8
Sufficient

S2:a+2=a+25% of a, But it can be decreasing also
Insufficient

:please Please provide Kudos, if you find my explanation good enough :please

Originally posted by rajatchopra1994 on 19 Nov 2019, 20:23.
Last edited by rajatchopra1994 on 20 Nov 2019, 04:39, edited 1 time in total.
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Re: The top surface area of a square tabletop was changed so that one of t  [#permalink]

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New post 20 Nov 2019, 04:33

Official solution:



S1:Let initial side of square=x
After changes,area=\((x-1)*(x+2)=70\)
solving we get, \(x^2+x-72 = 0\)
or, \((x-8)(x+9)= 0\)
or, \(x \)= 8 or -9
since, the dimension cannot be negative, x = 8
SUFFICIENT

S2: there was 25% change in one of the dimension
if there is 25 % increase, that means 25% of x = 2 or x = 8
if there is 25% decrease, that means 25% of x = 1 or x = 4.
Hence INSUFFICENT

Answer = A


gmatbusters wrote:
The top 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 change in one of the dimensions.


GMATbuster's Collection

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Re: The top surface area of a square tabletop was changed so that one of t   [#permalink] 20 Nov 2019, 04:33
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