If zt < -3, is z < 4 ? (1) z < 9 (2) t < -4

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anticipation: Junior | Next Rank: 30 Posts; Posts: 16; Joined: Mon Oct 26, 2009 4:52 am

by anticipation » Sun Dec 12, 2010 6:05 am

If zt < -3, is z < 4 ?

(1) z < 9
(2) t < -4

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Source: Beat The GMAT — Data Sufficiency | Sun Dec 12, 2010 6:05 am

prachich1987: Legendary Member; Posts: 752; Joined: Sun Sep 12, 2010 2:47 amFollowed by: 10 members; Thanked: 20 times; GMAT Score:700

by prachich1987 » Sun Dec 12, 2010 6:26 am

I think the answer should be "E"

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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Sun Dec 12, 2010 6:45 am

anticipation wrote:If zt < -3, is z < 4 ?

(1) z < 9
(2) t < -4

zt < -3 { we judge that one has to be negative and other one has to be positive}

is z < 4 ( we rewrite this as is 0 < z < 4 { is z positive } or 0 > z { or z negative } )

(1) z < 9

It can be any value either positive or negative

insufficient

( 2 ) t < -4

t is negative , so z has to be positive

But still it can be greater or less than 4

so should plug in some values.

t = -5 , z = 6 tz = -30

t = -6 , z = 1 tz = -6

in both the tz is less than -3 and the value of z can be less than or greater than 4

so insufficient

Even by considering both the statements, condition is still the same,

so my answer is E,

Saurabh Goyal
[email protected]
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EveryBody Wants to Win But Nobody wants to prepare for Win.

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mensanumber: Senior | Next Rank: 100 Posts; Posts: 31; Joined: Wed Oct 23, 2013 6:43 amFollowed by: 1 member; Thanked: 2 times; GMAT Score:750

by mensanumber » Fri Jun 20, 2014 11:26 pm

Hi Ron, Mitch, Brent and other experts:

When you guys do this(number picking) it seems so easy! However, number picking is my Achilles' Heel. It is just so frustratingly difficult for me to come up with right numbers.

When I micro-analyze my thinking process while I try to come up with right values to show counter examples this is what I see: I first need to ensure z <9 and then make sure that t < -4 and then ensure that zt< -3 with the aim of getting a NO for z<4. Even though I am using 'then' after every decision, the fact is- to generate right values, you essentially need to make these 4 decisions simultaneously. I simply dont know how I can do this in 20-30 seconds without befuddling my short term memory apparatus. I am saying 20-30 secs cuz in most of the hard questions you will have to rule out st-A, st-B and A+B as it comes down to E/C. thus you will make 5-6 such decisions for every question.

When I solve such questions I am either totally flustered or take more than 4 mins. Are there efficient ways to do this and which will work for most of the hard problems (inequality, modulus, reciprocal, neg/pos and their combination) etc..in less than 2-3 mins?
Thanks!

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Sat Jun 21, 2014 2:19 am

mensanumber wrote:Hi Ron, Mitch, Brent and other experts:

When you guys do this(number picking) it seems so easy! However, number picking is my Achilles' Heel. It is just so frustratingly difficult for me to come up with right numbers.

When I micro-analyze my thinking process while I try to come up with right values to show counter examples this is what I see: I first need to ensure z <9 and then make sure that t < -4 and then ensure that zt< -3 with the aim of getting a NO for z<4. Even though I am using 'then' after every decision, the fact is- to generate right values, you essentially need to make these 4 decisions simultaneously. I simply dont know how I can do this in 20-30 seconds without befuddling my short term memory apparatus. I am saying 20-30 secs cuz in most of the hard questions you will have to rule out st-A, st-B and A+B as it comes down to E/C. thus you will make 5-6 such decisions for every question.

When I solve such questions I am either totally flustered or take more than 4 mins. Are there efficient ways to do this and which will work for most of the hard problems (inequality, modulus, reciprocal, neg/pos and their combination) etc..in less than 2-3 mins?
Thanks!

When given a threshold, test EXTREMES: one value close to the threshold, one value far from the threshold.

If zt < -3, is z < 4 ?

(1) z < 9
(2) t < -4

In statement 1, the threshold for z is 9.

Case 1: z=8
Since zt < -3, we get:
8t < -3
t < -3/8.
Thus, it's possible that z=8 and t=-5.
In this case, both statements are satisfied and z>4.

Case 2: z=1
Since zt < -3, we get:
(1)(t) < -3
t < -3.
Thus, it's possible that z=1 and t=-5.
In this case, both statements are satisfied and z<4.

Thus, the two statements combined are INSUFFICIENT.

The correct answer is E.

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