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Please Help on this PS

by srini1988 » Tue Jul 26, 2011 8:36 pm
Hi,

Can anyone please help me to solve this PS.

If it is true that -6<=n<=10. Which of the following must be true?

1. n<8
2. n=-6
3. n>-8
4.-10<n<7
5. None of the above
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by Anurag@Gurome » Tue Jul 26, 2011 9:15 pm
srini1988 wrote:If it is true that -6<=n<=10. Which of the following must be true?

1. n<8
2. n=-6
3. n>-8
4.-10<n<7
5. None of the above
-6 ≤ n ≤ 10

(1) If n = 9, then n < 8 is not true.
(2) If n = 9, then n = -6 is not true.
(3) As n is between -6 and 10 inclusive, n is definitely greater than -8. Hence, n > -8 is true.
(4) We don't need to check this but again if we take n = 9, option 4 doesn't hold.

Therefore, the correct answer is 3.
Last edited by Anurag@Gurome on Thu Jul 28, 2011 4:54 am, edited 1 time in total.
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by srini1988 » Tue Jul 26, 2011 9:34 pm
Thanks Anurag
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by Frankenstein » Tue Jul 26, 2011 9:39 pm
Anurag@Gurome wrote:
srini1988 wrote:Hi,

Can anyone please help me to solve this PS.

If it is true that -6<=n<=10. Which of the following must be true?

1. n<8
2. n=-6
3. n>-8
4.-10<n<7
5. None of the above
-6 ≤ n ≤ 10

(1) If n = 9 or 10 or any fractional value greater than 8 and less than 10, then n < 8 is not true.
(2) If n is any other value between -6 ≤ n ≤ 10, then n = -6 is not true.
(3) If n = - 7, then it does not satisfy -6 ≤ n ≤ 10. Hence, n > -8 is not true.
(4) -10 < n < 7 implies n can be -9, -8, -7 or any fractional value so that -10 < n ≤ -6, which contradicts -6 ≤ n ≤ 10. Hence, not true again.

Therefore, the correct answer is 5.
Hi,
It says that -6<=n<=10 is true. So, we cannot consider n=-7 which is the not in the range.
So, whatever be the value of n in the given range, it will be greater than -8. So, C should be fine. Could you comment on this.
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by Anurag@Gurome » Tue Jul 26, 2011 9:42 pm
Edit : Post deleted.
Last edited by Anurag@Gurome on Thu Jul 28, 2011 4:55 am, edited 2 times in total.
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by abhisays » Tue Jul 26, 2011 9:44 pm
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by Frankenstein » Tue Jul 26, 2011 9:48 pm
Anurag@Gurome wrote: Option 3 says n > -8, which means n can take any value greater than -8, which can be -7 also. We cannot apply the given condition here, rather looking at the given condition -6 ≤ n ≤ 10, we have check which of the given options is true. I hope it helps.
Hi,
No. My point is different.
All we know is -6<=n<=10 is true. So, whatever the value of 'n' we pick from this range it will be greater than -8. For E to be the answer, we have to show that there exists a value 'n' in the range [-6,10], but it doesn't satisfy any of the options A to D. Picking n=-7 doesn't serve the purpose because that value does not satisfy the necessary condition of -6<=n<=10.
So, the answer to this question should be C.
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by ntamhane » Wed Jul 27, 2011 10:46 am
@Frankenstein - I agree with your answer
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by gratuscm » Wed Jul 27, 2011 11:57 am
Frankenstein and Ntamhane, I agree as well. If it is given that N is greater than or equal to -6 and less than or equal to 10, we can conclude that N must be greater than -8. It is also true that N must be greater than -7. Both statements are correct.
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by mayank.arora » Thu Jul 28, 2011 2:12 am
No frankestien, you're getting it wrong, the question asks which of the following 'must' be true, picking up option 'd' suggests we can take any value greater than -8, this can be anything between -8 and infinity, so try and pick up 255, it doesn't satisfy the given condition.
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by jrodriguezblanco » Thu Jul 28, 2011 2:24 am
Hi guys,
I agree with Anurag. By picking -7 (c), you're checking the choice against the stem. But that's wrong, you have to check the stem against the choice. If you pick n=11, it does agree with c, but not with the condition. So C "must" not be true.
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by Frankenstein » Thu Jul 28, 2011 3:50 am
mayank.arora wrote:No frankestien, you're getting it wrong, the question asks which of the following 'must' be true, picking up option 'd' suggests we can take any value greater than -8, this can be anything between -8 and infinity, so try and pick up 255, it doesn't satisfy the given condition.
Hi,
My option was C. Your 'D' must have been typo. Btw, you are doing the same mistake. 255 doesn't satisfy the given condition -6<= n <= 10. How can you use that as an example. The questions is pretty clear, every number in the range [-6,10] is definitely -8. You guys are trying to prove the converse. We don't need every number greater than -8 to be in the range [-6,10]. Try to think about it again.

Same is the case with Rodriguezblanco.
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by vipin85 » Thu Jul 28, 2011 4:00 am
srini1988 wrote:Hi,

If it is true that -6<=n<=10. Which of the following must be true?

1. n<8
2. n=-6
3. n>-8
4.-10<n<7
5. None of the above
I would go with option C as well.
Here is the reasoning.

The question asks which of the following must be true or in other words, which of the answer options cover the entire range of possible values for -6<=n<=10

A: Does not cover 8,9 and 10. Hence ruled out
B: Rules out everything except -6. Hence ruled out
C: Covers all values for n between -6 and 10. This condition must be true if 6<=n<=10 is true. A valid answer choice
D: Rules out 7,8,9 and 10
E: Ruled out since C is a possible choice
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by mayank.arora » Thu Jul 28, 2011 4:07 am
Frankestien: agreed....
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by Anurag@Gurome » Thu Jul 28, 2011 4:51 am
Hi everyone!
The explanation provided by Frankenstein is indeed correct. The previous explanation provided by me are wrong. I'm editing my first post.
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