Sure!
S1::
z < 9
So it might be less than 4, it might not be. INSUFFICIENT.
A fuller explanation:
If z < -3, and z < 9, then t * (<9) < -3. Since we don't know if z is positive or negative, we can't really do much with this inequality.
S2::
t < -4
Now we KNOW that t is negative. If have zt < -3, and we divide both sides by t, a negative number, our question becomes z > (-3)/t. But what's t? We don't know, so this is not helpful.
S1 and S2::
We have (-3)/t < z < 9. Is z greater than 4? We can't say.
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tough question
Source: Beat The GMAT — Data Sufficiency |
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Hi semwal,
This types of DS questions are perfect for TESTing values and tracking the results.
Here, we're told that zt < -3
There's a Number Property at play here: this means that one of the variables is positive and one is negative. They can't both be negative and they can't both be positive (and neither can be = 0).
The question asks "is z < 4?"
Fact 1 tells us that z < 9
Let's TEST values:
t = -1
z = 8
These values fit all the facts that we have; the answer to the question would be NO
Now, let's keep the t and change the z:
t = -1
z = 3.5
These values fit all the facts that we have; the answer to the question would be YES
Inconsistent answers = INSUFFICIENT
Fact 2 tells us that t < -4
Let's TEST...
t = -5
z = 10
These values fit all the facts that we have; the answer to the question would be NO
Now, let's keep the t and change the z:
t = -5
z = 3
These values fit all the facts that we have; the answer to the question would be YES
Inconsistent answers = INCONSISTENT
Combing Facts, we know that the t is negative (from Fact 2), so the z MUST be positive (from the info in the prompt).
We don't know HOW POSITIVE though. Z could be small (YES answer) or big (NO answer)
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
This types of DS questions are perfect for TESTing values and tracking the results.
Here, we're told that zt < -3
There's a Number Property at play here: this means that one of the variables is positive and one is negative. They can't both be negative and they can't both be positive (and neither can be = 0).
The question asks "is z < 4?"
Fact 1 tells us that z < 9
Let's TEST values:
t = -1
z = 8
These values fit all the facts that we have; the answer to the question would be NO
Now, let's keep the t and change the z:
t = -1
z = 3.5
These values fit all the facts that we have; the answer to the question would be YES
Inconsistent answers = INSUFFICIENT
Fact 2 tells us that t < -4
Let's TEST...
t = -5
z = 10
These values fit all the facts that we have; the answer to the question would be NO
Now, let's keep the t and change the z:
t = -5
z = 3
These values fit all the facts that we have; the answer to the question would be YES
Inconsistent answers = INCONSISTENT
Combing Facts, we know that the t is negative (from Fact 2), so the z MUST be positive (from the info in the prompt).
We don't know HOW POSITIVE though. Z could be small (YES answer) or big (NO answer)
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
-
GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Location: New York, NY
- Thanked: 13060 times
- GMAT Score:790
When a DS problem gives a THRESHOLD, try values CLOSE to the threshold and FAR from the threshold.semwal wrote:dear all,
could u help me solve this;
If zt < -3, is z < 4?
a. z < 9
b. t < -4
Here, the threshold for t is -4, while the threshold for z is 9.
Case 1: t = -5 and z=8
Statement 2: t < -4.
Statement 1: z < 9.
Question stem: zt = -5*8 = -40, which is less than -3.
In this case, z > 4.
Case 2: t = -5 and z=2
Statement 2: t < -4.
Statement 1: z < 9.
Question stem: zt = -5*2 = -10, which is less than -3.
In this case, z<4.
Since z>4 in the first case and z<4 in the second case, the two statements combined are INSUFFICIENT.
The correct answer is E.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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