Inequalities --> m + z > 0

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Gdieterling: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Thu Aug 06, 2009 8:20 am; Thanked: 2 times

by Gdieterling » Thu Sep 03, 2009 10:51 am

Hello guys, here is a question for you :

Is m + z > 0 ?

1) m - 3z > 0
2) 4z - m > 0

OA : [spoiler]Not sure anymore ... stupid me, I think it was B ![/spoiler]

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Source: Beat The GMAT — Data Sufficiency | Thu Sep 03, 2009 10:51 am

navalpike: Master | Next Rank: 500 Posts; Posts: 103; Joined: Mon May 04, 2009 11:53 am; Thanked: 6 times

by navalpike » Thu Sep 03, 2009 11:26 am

I'll take a shot at it. I'd go with C.

Question is asking if m >-z

1. m > 3z
This could be easily true if z were positive. However, if we imagine that z is -1, then,
M > 3(-1)
m>-3
but then the question is asking
Is m > 1
which is not necessarily true.

2. 4z>m
Just take z as 1. Just because m is less than 4 does not mean that m is greater than -1.

1+2

When we combine the two inqualities in S1 and S2, we get z > 0
We also have 3z<m<4z
Thus, we see that z is positive, which makes m positive. And if m is positive, it will be greater than -z.

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Gdieterling: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Thu Aug 06, 2009 8:20 am; Thanked: 2 times

by Gdieterling » Thu Sep 03, 2009 12:20 pm

Thanks

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