Rectangular swimming pool

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Vemuri: Legendary Member; Posts: 682; Joined: Fri Jan 16, 2009 2:40 am; Thanked: 32 times; Followed by:1 members

Rectangular swimming pool

by Vemuri » Sat Feb 21, 2009 10:24 pm

I have a rectangular swimming pool with dimensions 10×40. Now I want to build a deck of uniform width surrounding the pool so that I can get in and out. If I want the total area of the deck to equal the area of the pool, what should the width of my deck be?

A. 3.5
B. 5.5
C. 1
D. 7
E. 8.5

OA is A. Can someone please explain?

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Source: Beat The GMAT — Problem Solving | Sat Feb 21, 2009 10:24 pm

x2suresh: Master | Next Rank: 500 Posts; Posts: 258; Joined: Thu Aug 07, 2008 5:32 am; Thanked: 16 times

Re: Rectangular swimming pool

by x2suresh » Sat Feb 21, 2009 10:32 pm

Vemuri wrote:I have a rectangular swimming pool with dimensions 10×40. Now I want to build a deck of uniform width surrounding the pool so that I can get in and out. If I want the total area of the deck to equal the area of the pool, what should the width of my deck be?

A. 3.5
B. 5.5
C. 1
D. 7
E. 8.5

OA is A. Can someone please explain?

Let W is width of DECK

(10+2w)*(40+2w) = 400+400 = 800

when 2w = 7 (10+2w)*(40+2w) = 799

w= 3.5

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Vemuri: Legendary Member; Posts: 682; Joined: Fri Jan 16, 2009 2:40 am; Thanked: 32 times; Followed by:1 members

Re: Rectangular swimming pool

by Vemuri » Sat Feb 21, 2009 11:18 pm

x2suresh wrote:
Vemuri wrote:I have a rectangular swimming pool with dimensions 10×40. Now I want to build a deck of uniform width surrounding the pool so that I can get in and out. If I want the total area of the deck to equal the area of the pool, what should the width of my deck be?

A. 3.5
B. 5.5
C. 1
D. 7
E. 8.5

OA is A. Can someone please explain?
Let W is width of DECK

(10+2w)*(40+2w) = 400+400 = 800

when 2w = 7 (10+2w)*(40+2w) = 799

w= 3.5

IMO Thanks. I think I am having difficulty understanding the question. What was your premise for adding 2w to the dimension of the swimming pool?

Quote

x2suresh: Master | Next Rank: 500 Posts; Posts: 258; Joined: Thu Aug 07, 2008 5:32 am; Thanked: 16 times

Re: Rectangular swimming pool

by x2suresh » Sat Feb 21, 2009 11:28 pm

Vemuri wrote:
x2suresh wrote:
Vemuri wrote:I have a rectangular swimming pool with dimensions 10×40. Now I want to build a deck of uniform width surrounding the pool so that I can get in and out. If I want the total area of the deck to equal the area of the pool, what should the width of my deck be?

A. 3.5
B. 5.5
C. 1
D. 7
E. 8.5

OA is A. Can someone please explain?
Let W is width of DECK

(10+2w)*(40+2w) = 400+400 = 800

when 2w = 7 (10+2w)*(40+2w) = 799

w= 3.5
IMO Thanks. I think I am having difficulty understanding the question. What was your premise for adding 2w to the dimension of the swimming pool?

Visualize this way..

Rectangle (SP) in side Big rectangle.

wwwwwwwwww
w---------------w
w
w---------------w
wwwwwwwwww

Area of Outer rectangle = (10+2w)*(40+2w)

Its mention the Deck area = SP area

Deck Area =Area Big Rectange - SP Rectangle Aea

Big Rectagle area = Deck Area + SP area = 2*SP Area = 2*400

I hope it is clear now.

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Vemuri: Legendary Member; Posts: 682; Joined: Fri Jan 16, 2009 2:40 am; Thanked: 32 times; Followed by:1 members

Re: Rectangular swimming pool

by Vemuri » Sun Feb 22, 2009 5:23 am

Yep, I think I am now clear on what the question is asking. But, can you explain the below calculation in your response?

(10+2w)*(40+2w) = 400+400 = 800 --> I understood this part

when 2w = 7 (10+2w)*(40+2w) = 799

w= 3.5

Appreciate your response

& sorry for being such a dumbo.

Quote

x2suresh: Master | Next Rank: 500 Posts; Posts: 258; Joined: Thu Aug 07, 2008 5:32 am; Thanked: 16 times

Re: Rectangular swimming pool

by x2suresh » Sun Feb 22, 2009 6:05 am

Vemuri wrote:Yep, I think I am now clear on what the question is asking. But, can you explain the below calculation in your response?

(10+2w)*(40+2w) = 400+400 = 800 --> I understood this part

when 2w = 7 (10+2w)*(40+2w) = 799

w= 3.5

Appreciate your response & sorry for being such a dumbo.

(10+2w)*(40+2w) =800
we need to solve the above equation to get w.

I substitued values from Answer choices.

when w= 3.5 i.e 2w=7

(10+2w)*(40+2w) = 799~800

This is the Answer.

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mjjking: Master | Next Rank: 500 Posts; Posts: 353; Joined: Sat Jan 20, 2007 1:29 am; Location: Italy; Thanked: 7 times; GMAT Score:720

by mjjking » Mon Feb 23, 2009 3:10 am

JUST A QUESTION: what is the source of this?
I do not question the type of question but the values you find... very gmat-unlike

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