Inequalities Problem

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jeffboshine: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Tue Feb 09, 2010 8:31 am; Thanked: 1 times

by jeffboshine » Sat Mar 31, 2012 2:54 pm

If zt < -3, is Z<4?

I) Z<9
II) t<-4

I came up with B as answer. That was wrong. The answer is E.

If T<-4, Then Z > 1/2 (if Z = -6) and Z > 1/10 (if Z = -30). Wouldn't that make II sufficient?

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Source: Beat The GMAT — Data Sufficiency | Sat Mar 31, 2012 2:54 pm

Bill@VeritasPrep: GMAT Instructor; Posts: 1248; Joined: Thu Mar 29, 2012 2:57 pmFollowed by: 192 members; Location: Everywhere; Thanked: 503 times; GMAT Score:780

by Bill@VeritasPrep » Sat Mar 31, 2012 3:01 pm

In statement 2, t could be -5 and z could be 6, which gives you a product of -30 and an answer of no, z is not less than 4.

T could be -5 and z could be 2, which gives you a product of -10 and an answer of yes, z is greater than 4.

Since we can get a yes and a no, it is insufficient.

Bill

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sun Apr 01, 2012 9:15 pm

jeffboshine wrote:If zt < -3, is Z<4?

I) Z<9
II) t<-4

I came up with B as answer. That was wrong. The answer is E.

If T<-4, Then Z > 1/2 (if Z = -6) and Z > 1/10 (if Z = -30). Wouldn't that make II sufficient?

If zt < -3, is z < 4?

(1) z < 9
If z = 5, t = -5, then zt = -25, which is < -3. Here z > 4.
If z = 3, t = -5, then zt = -15, which is < -3. Here z < 4.
No definite answer; NOT sufficient.

(2) t < -4, taking the same examples in statement 1.
If z = 5, t = -5, then zt = -25, which is < -3. Here z > 4.
If z = 3, t = -5, then zt = -15, which is < -3. Here z < 4.
No definite answer; NOT sufficient.

Combining (1) and (2), again we take the same examples, so there is no additional info; NOT sufficient.

The correct answer is E.

Anurag Mairal, Ph.D., MBA
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