Fractional part of total surface area

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mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Sun Jun 01, 2008 12:39 am

S2-16 What fractional part of the total surface area of cube C is red?

(1) Each of 3 faces of C is exactly red.
(2) Each of 3 faces of C is entirely white.

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Source: Beat The GMAT — Data Sufficiency | Sun Jun 01, 2008 12:39 am

amitansu: Master | Next Rank: 500 Posts; Posts: 294; Joined: Tue Feb 26, 2008 9:05 pmFollowed by: 1 member; Thanked: 13 times

by amitansu » Sun Jun 01, 2008 9:10 am

A should be ans here.

From 1 : surface area of red face=3a^2 (assume a is side)
total surface area=6a^2

so sufficient
From 2:no idea about red face.so insufficient.

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mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Mon Jun 02, 2008 2:08 am

Hey Amit,

There is small mistake, please read the question below -

S2-16 What fractional part of the total surface area of cube C is red?

(1) Each of 3 faces of C is exactly 1/2 red.
(2) Each of 3 faces of C is entirely white.

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amitansu: Master | Next Rank: 500 Posts; Posts: 294; Joined: Tue Feb 26, 2008 9:05 pmFollowed by: 1 member; Thanked: 13 times

by amitansu » Mon Jun 02, 2008 4:04 am

Still A would be ans.Since data about exact red face is given.

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mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Tue Jun 03, 2008 2:51 am

OA is - 'C'

amitansu wrote:Still A would be ans.Since data about exact red face is given.

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molt_llest: Senior | Next Rank: 100 Posts; Posts: 69; Joined: Sat May 10, 2008 3:05 pm; Thanked: 1 times

by molt_llest » Tue Jun 03, 2008 3:09 am

I would say is C because in (1) we know that 1,5 out of 3 faces are red but we don't know wether the other 3 gfaces are red. In (2) we don't know anything about the red faces. Putting togheter (1) and (2) we know the colour of the 6 faces.

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mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Tue Jun 03, 2008 1:52 pm

Yeah...!! I think explanation is very logical. We don't need to put formulas to solve this question.

molt_llest wrote:I would say is C because in (1) we know that 1,5 out of 3 faces are red but we don't know wether the other 3 gfaces are red. In (2) we don't know anything about the red faces. Putting togheter (1) and (2) we know the colour of the 6 faces.

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