Gmat Prep Question Please help - Area of a square garden - The Beat The GMAT Forum

Gmat Prep Question Please help - Area of a square garden

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dubeystuts: Senior | Next Rank: 100 Posts; Posts: 72; Joined: Sat Aug 23, 2008 3:26 am; Thanked: 1 times

by dubeystuts » Sat Jan 17, 2009 10:50 am

Area of a square garden in A square feet and perimeter is P feet. If
A = 2P + 9 what is the perimeter of the garden in feet?

1) 28
2) 36
3) 40
4) 56
5) 64

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Source: Beat The GMAT — Problem Solving | Sat Jan 17, 2009 10:50 am

DanaJ: Site Admin; Posts: 2567; Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members; Thanked: 712 times; GMAT Score:770

by DanaJ » Sat Jan 17, 2009 11:00 am

Let's say that x is the length of one side of the garden.
A = x^2
P = 4x
Then you have: A = 2P + 9, which means that x^2 = 8x+9. That is the equivalent of x^2 - 8x - 9 = 0. That in turn is the equivalent of (x - 9)(x +1) = 0. That gives us x = 9 or x = -1. Since x is the length of a side, it can only be positive. So x = 9. P will be 4*9 = 36.

Answer: B.

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dubeystuts: Senior | Next Rank: 100 Posts; Posts: 72; Joined: Sat Aug 23, 2008 3:26 am; Thanked: 1 times

by dubeystuts » Sat Jan 17, 2009 11:46 am

Thank You very much.

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deepoe: Master | Next Rank: 500 Posts; Posts: 151; Joined: Wed Feb 11, 2009 2:45 am; Thanked: 3 times

by deepoe » Tue May 05, 2009 12:07 am

I don't understand the 8x :$

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DanaJ: Site Admin; Posts: 2567; Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members; Thanked: 712 times; GMAT Score:770

by DanaJ » Tue May 05, 2009 1:03 am

A = 2P + 9

P = 4x or four times the length of one side, meaning that 2P + 9 = 2*4x + 9 = 8X + 9

A = x^2 - area of square

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deepoe: Master | Next Rank: 500 Posts; Posts: 151; Joined: Wed Feb 11, 2009 2:45 am; Thanked: 3 times

by deepoe » Tue May 05, 2009 1:57 am

Ooohhh ok ok! you already did 4 times in the equation :$ nThanks!

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