Data Sufficiency Question - Easy but a challenging assumptio - The Beat The GMAT Forum

Data Sufficiency Question - Easy but a challenging assumptio

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Ankush Soni: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Mon Sep 22, 2008 8:25 am

by Ankush Soni » Mon Sep 22, 2008 8:33 am

Q: A rectangle has length, width and diagonal as L, W and D resp. What is the length of the rectangle ?

1. L+W = 6
2. D^2 = 20 i.e D to the power of 2 = 20

Which choice would you mark (C) or (E). Thanks.
My assumption is the length of a rectangle is always the longest side.

Thanks

Ankush

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Source: Beat The GMAT — Data Sufficiency | Mon Sep 22, 2008 8:33 am

tendays2go: Senior | Next Rank: 100 Posts; Posts: 55; Joined: Sun Sep 14, 2008 6:51 am; Location: Netherlands; Thanked: 10 times; GMAT Score:680

by tendays2go » Mon Sep 22, 2008 9:32 am

if D^2 = 20 => L^2 + W^2 = 20
Also, L+W = 6 => L^2 + W^2 + 2L*W = 36 i.e. L*W = 8
so, we have L* ( 6 - L) = 8 or L=2/4

now, the question says clearly that L is the length, so for me,
L = 4 is the correct answer.

What is the OA?

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4meonly: Legendary Member; Posts: 891; Joined: Sat Aug 16, 2008 4:21 amFollowed by: 1 member; Thanked: 27 times; GMAT Score:660(

by 4meonly » Mon Sep 22, 2008 9:56 am

NEither 1 nor 2 alone are not suff

Combining:
we have
l+w=6, w=6-l
d^2=20
l^2 + (6-l)^2 = 20 solving we get
l^2 - 6l + 8 = 0
(l-2)(l-4)=0
l can be as 2 as 4, so I think answer wil be E until we are told that l>w.

I don't know whether lenght is always more than width in GMAT
Can anybody resolve my doubts?
I will choose E in this case

I think we need Stuart and Ian here!

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Ankush Soni: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Mon Sep 22, 2008 8:25 am

Hi Tendaysago and 4meonly

by Ankush Soni » Mon Sep 22, 2008 11:47 am

answering to ten days ago
......the original question was what is the area of the rectangle ?
I just extended the question to calculating the length.

answering to 4meonly

How do we get Stuart or Ian here ?

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mals24: Legendary Member; Posts: 683; Joined: Tue Jul 22, 2008 1:58 pmFollowed by: 2 members; Location: Dubai; Thanked: 73 times

by mals24 » Mon Sep 22, 2008 11:49 am

Agree with 4meonly the answer should be E

The length of a rectangle is not necessarily greater than the width. So L could be 2 or 4.

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mals24: Legendary Member; Posts: 683; Joined: Tue Jul 22, 2008 1:58 pmFollowed by: 2 members; Location: Dubai; Thanked: 73 times

by mals24 » Mon Sep 22, 2008 11:55 am

@ Ankush Soni

If the question is asking for area of the rectangle then the answer is clearly C. The solution is explained very clearly by tendays2go

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GMAT/MBA Expert

Ian Stewart: GMAT Instructor; Posts: 2623; Joined: Mon Jun 02, 2008 3:17 amFollowed by: 355 members; Location: Montreal; Thanked: 1090 times; GMAT Score:780

by Ian Stewart » Mon Sep 22, 2008 2:38 pm

The 'length' of a rectangle is normally equal to its longest side, so the answer here should be C, as I think has been explained adequately above. Still, the GMAT does *not* test whether you know obscure details about mathematical definitions. There is no chance that you would see a question exactly like this on the GMAT- if it were a real GMAT question, they would tell you that l > w. So don't worry about the minor technicality here that makes the answer C; if you found that 2 and 4 are the two side lengths, you've learned what you need to from the question.

For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com

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Ankush Soni: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Mon Sep 22, 2008 8:25 am

Hi

by Ankush Soni » Wed Sep 24, 2008 10:42 am

Thanks Ian

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