relation between x>y>z

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ifthyder: Master | Next Rank: 500 Posts; Posts: 118; Joined: Fri Apr 18, 2008 4:58 am; Thanked: 1 times

by ifthyder » Fri Sep 26, 2008 8:49 am

how do we know about y ?

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Source: Beat The GMAT — Data Sufficiency | Fri Sep 26, 2008 8:49 am

Morgoth: Master | Next Rank: 500 Posts; Posts: 316; Joined: Mon Sep 22, 2008 12:04 amFollowed by: 1 member; Thanked: 36 times

Re: relation between x>y>z

by Morgoth » Fri Sep 26, 2008 9:05 am

ifthyder wrote:how do we know about y ?

x>y>z ?

1) xz>yz, since x y and z are positive numbers we can simplify this
x>y. we dont know anything about z. Insufficient.

2) yx>yz, since x y and z are positive numbers we can simplify this
x>z, we dont know anything about y. Insufficient.

Combining 1 & 2

We still dont know about the relationship between z and y. Insufficient.

Thus, E is the answer.

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kuroneko1313: Senior | Next Rank: 100 Posts; Posts: 35; Joined: Thu Aug 21, 2008 2:55 pm; Thanked: 1 times

by kuroneko1313 » Fri Sep 26, 2008 10:46 am

I think it's E too, agree with Morgoth's explanation.

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sumithshah: Master | Next Rank: 500 Posts; Posts: 165; Joined: Wed May 28, 2008 11:25 pm; Thanked: 9 times; GMAT Score:730

by sumithshah » Tue Sep 30, 2008 10:02 am

Subtract 1 from 2, you shall get

xz-yx>0

x(z-y)>0

therefore, either both x and z-y>0 or x and z-y <0
but we know X>0 ( x is given as positive) hence z-y>0, z>y.

Hence C

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EricLien9122: Master | Next Rank: 500 Posts; Posts: 106; Joined: Thu May 22, 2008 10:50 am; Thanked: 3 times

by EricLien9122 » Tue Sep 30, 2008 11:54 am

sumithshah:

I don't think you can subtract inequality equations.

Please share your thoughts.

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gabriel: Legendary Member; Posts: 986; Joined: Wed Dec 20, 2006 11:07 amFollowed by: 1 member; Location: India; Thanked: 51 times

by gabriel » Tue Sep 30, 2008 1:40 pm

EricLien9122 wrote:sumithshah:

I don't think you can subtract inequality equations.

Please share your thoughts.

You can subtract inequality equations. But there are some operations like multiplication, division and squaring that you can do only after considering the sign of the variables in question.

Cheers.

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schumi_gmat: Master | Next Rank: 500 Posts; Posts: 377; Joined: Wed Sep 03, 2008 9:30 amFollowed by: 2 members; Thanked: 15 times

by schumi_gmat » Tue Sep 30, 2008 1:42 pm

what is the OA

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kris610: Master | Next Rank: 500 Posts; Posts: 198; Joined: Fri Mar 09, 2007 8:40 pm; Thanked: 7 times

by kris610 » Wed Oct 01, 2008 11:58 am

sumithshah wrote:Subtract 1 from 2, you shall get

xz-yx>0

x(z-y)>0

therefore, either both x and z-y>0 or x and z-y <0
but we know X>0 ( x is given as positive) hence z-y>0, z>y.

Hence C

I can subract the other way around, in which case I would get y>z.

I think it is E.

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