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Bunuel
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If –8 < k < 8, is k < –2 ? 14 Mar 2017, 03:45
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

65% (hard)

Question Stats:

56% (02:14) correct 44% (02:04) wrong based on 98 sessions

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If –8 < k < 8, is k < –2 ?

(1) k^2 – 7k – 18 > 0
(2) 1/k < 1/2
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A
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rohit8865
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If –8 < k < 8, is k < –2 ? Updated on: 14 Mar 2017, 19:05
Originally posted by rohit8865 on 14 Mar 2017, 07:47.
Last edited by rohit8865 on 14 Mar 2017, 19:05, edited 2 times in total.
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Bunuel
If –8 < k < 8, is k < –2 ?

(1) k^2 – 7k – 18 > 0
(2) 1/k < 1/2
Show more


(1) (k+2)(k-9)>0
or k<-2 and k>9
but as –8 < k < 8
then -8<k<-2
suff

(2) 1/k-1/2<0

2-k/2k<0
thus k>2 or k<0....insuff

combining we get
k>9 or k <0
insuff

Ans A
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If –8 < k < 8, is k < –2 ? 14 Mar 2017, 11:11
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1 is insufficient
2 is sufficient

1/k < 1/2
1 < 1/2k
k >2
OR

1/k - 1/2 < 0
(2-k)/2k < 0
2 - k < 0
k > 2

Answer is B
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If –8 < k < 8, is k < –2 ? 14 Mar 2017, 11:22
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rohit8865
Bunuel
If –8 < k < 8, is k < –2 ?

(1) k^2 – 7k – 18 > 0
(2) 1/k < 1/2


(1) (k+2)(k-9)>0
or k<2 and k>9
insuff

(2) 1/k-1/2<0

2-k/2k<0
thus k>2 or k<0....insuff

combining we get
k>9 or k <0
insuff

Ans E
Show more

I think you forgot that k is between -8 and 8

=> (1) If we simplify (k+2) * (k-9) > 0

=> k>9 or k<-2 => k must be smaller than -2 because k is between -8 and 8 => Sufficient

(2) k could be 6 or -4 for example (1/6< 1/2 and 1/(-4) < 1/2). => Insufficient

Answer A
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If –8 < k < 8, is k < –2 ? 14 Mar 2017, 19:00
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LHC8717
rohit8865
Bunuel
If –8 < k < 8, is k < –2 ?

(1) k^2 – 7k – 18 > 0
(2) 1/k < 1/2


(1) (k+2)(k-9)>0
or k<2 and k>9
insuff

(2) 1/k-1/2<0

2-k/2k<0
thus k>2 or k<0....insuff

combining we get
k>9 or k <0
insuff

Ans E

I think you forgot that k is between -8 and 8

=> (1) If we simplify (k+2) * (k-9) > 0

=> k>9 or k<-2 => k must be smaller than -2 because k is between -8 and 8 => Sufficient

(2) k could be 6 or -4 for example (1/6< 1/2 and 1/(-4) < 1/2). => Insufficient

Answer A
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BIG BLUNDER!

Edited!!
Anyway thanks

Answer must be A
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If –8 < k < 8, is k < –2 ? 14 Mar 2017, 19:05
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LHC8717 I understand the first one is sufficient. However why the second one is not sufficient. Explain. What am I doing wrong?
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If –8 < k < 8, is k < –2 ? 15 Mar 2017, 02:11
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St 1: (k-9)(k+2)>0.. therefore k<-2 or k>9. since -8<k<8. therefore k<-2. ANSWER
St 2: 1/k<1/2 or 1/k-1/2<0 or (2-k)/2k<0 or k>2 or k<0. INSUFFICIENT

Option A
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If –8 < k < 8, is k < –2 ? 15 Mar 2017, 04:45
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matthewsmith_89
LHC8717 I understand the first one is sufficient. However why the second one is not sufficient. Explain. What am I doing wrong?
Show more

You can use the method from the other answer to find k>2 or k<0 but for me that was time consuming.

The question ask if k is smaller than -2 or not (k<-2)

Then the second statement say that 1/k < 1/2 => 1/k must be smaller than 1/2 and therefore k must be higher than 2 or to be negative.

We know that k is between -8 and 8 and then I just took random number 6 and -4. Therefore we see that k could be higher or smaller than -2 then we cannot answer the question with this statement.

Hope you understand matthewsmith_89!
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If –8 < k < 8, is k < –2 ? 21 Apr 2021, 06:24
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