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Source: — Data Sufficiency |
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by givemeanid » Fri Jul 13, 2007 4:14 pm
1. z<9
z=3, t=-6. z<4. True
z=6, t=-6. z>4. False
INSUFFICIENT.

2. t<-4
z=3, t=-6. z<4. True
z=6, t=-6. z>4. False
INSUFFICIENT.

Combining:
Same values as used above.
INSUFFICIENT.

Answer is (E).
So It Goes
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by jayant.apte » Sun Mar 09, 2008 11:14 pm
The OA is E but I don't understand why the answer is not B. I think we should be able to take (2) and plug in values into zt < -3.

Using (2) say t = -6, we will get z x -6 < -3 which means z < 0.5 which is less than 4. Any value of t < -4 will result in z < 4 being satisfied. Am I missing something here?
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by tmmyc » Mon Mar 10, 2008 7:50 pm
It actually means z > 0.5, not z < 0.5.

When dividing by a negative number, you need to flip the sign of the inequality.

You can choose some numbers for peace of mind:

Assume z < 0.5
Choose z = 0

0 * -6 < -3
0 < -3 is not true


Assume z > 0.5
Choose z = 0

1* -6 < -3
-6 < -3 is true
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