21q17

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stubbornp: Master | Next Rank: 500 Posts; Posts: 496; Joined: Sun May 04, 2008 11:01 pm; Location: mumbai; Thanked: 7 times; GMAT Score:640

by stubbornp » Sat Oct 18, 2008 10:37 pm

17. What is the volume of a certain rectangular solid?
(1) Two adjacent faces of the solid have areas 15 and 24, respectively.
(2) Each of two opposite faces of the solid has area 40.

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Source: Beat The GMAT — Data Sufficiency | Sat Oct 18, 2008 10:37 pm

Saffa: Senior | Next Rank: 100 Posts; Posts: 41; Joined: Thu Jul 12, 2007 1:16 am; Location: Cape Town South Africa; Thanked: 5 times

by Saffa » Sun Oct 19, 2008 12:10 am

Both on their own is NOT SUFF as we don't have enough info:

Together:

Say Length = l, width = w and height = h

we're lloking for l x w x h = volume

but from (1): l x w = 15 and w x h = 24

from (2) l x h = 40

so now we have 3 unknowns with 3 equations, so you'll be able to work it out.

So IMO C.

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codesnooker: Legendary Member; Posts: 543; Joined: Fri Jan 18, 2008 1:01 am; Thanked: 43 times; GMAT Score:580

by codesnooker » Sun Oct 19, 2008 1:22 am

(A) should be the answer.

L x W = 24 = 8 x 3
W x H = 15 = 5 x 3

So when you factorize above both equation, you can figure out the value of W = 3.

Therefore H = 5 and L = 8.

Hence volume = 3 x 5 x 8

Hence (A) is alone sufficient.

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stubbornp: Master | Next Rank: 500 Posts; Posts: 496; Joined: Sun May 04, 2008 11:01 pm; Location: mumbai; Thanked: 7 times; GMAT Score:640

by stubbornp » Sun Oct 19, 2008 7:25 am

codesnooker wrote:(A) should be the answer.

L x W = 24 = 8 x 3
W x H = 15 = 5 x 3

So when you factorize above both equation, you can figure out the value of W = 3.

Therefore H = 5 and L = 8.

Hence volume = 3 x 5 x 8

Hence (A) is alone sufficient.

Codesnooker,Isn't there is one case L x W=24 = 24 x 1
W x H=15 x 1

here we can figure out W=1...what do you say?

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codesnooker: Legendary Member; Posts: 543; Joined: Fri Jan 18, 2008 1:01 am; Thanked: 43 times; GMAT Score:580

by codesnooker » Sun Oct 19, 2008 7:55 am

stubbornp wrote:
codesnooker wrote:(A) should be the answer.

L x W = 24 = 8 x 3
W x H = 15 = 5 x 3

So when you factorize above both equation, you can figure out the value of W = 3.

Therefore H = 5 and L = 8.

Hence volume = 3 x 5 x 8

Hence (A) is alone sufficient.

Codesnooker,Isn't there is one case L x W=24 = 24 x 1
W x H=15 x 1

here we can figure out W=1...what do you say?

Hmm. You are correct. My apologizes for the mistake.

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gmattakers: Junior | Next Rank: 30 Posts; Posts: 25; Joined: Wed Oct 29, 2008 7:26 pm

by gmattakers » Thu Oct 30, 2008 4:39 pm

I think both 1 and 2 are needed

Taking the GMAT

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