Dear All
Here is a DS - Is n be divisible by 4
As the attached picture.
My answer is B, I disagree with statement #1 is sufficient,
cuz I have an example:
if N square = 64, obviously is divisible by 8, than n square root = 4√2 ̄, obviously, it is not divisible by 4, so my answer is insufficient.
any wrong here?
please help
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DS - Is n be divisible by 4
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Hi zoe,
Can you post the full question (or type it out)? The image file that you attached doesn't link to an image.
GMAT assassins aren't born, they're made,
Rich
Can you post the full question (or type it out)? The image file that you attached doesn't link to an image.
GMAT assassins aren't born, they're made,
Rich
Ok,[email protected] wrote:Hi zoe,
Can you post the full question (or type it out)? The image file that you attached doesn't link to an image.
GMAT assassins aren't born, they're made,
Rich
I didn't input the whole question yesterday because I did not know how to input some math marks.
Maybe input the whole question and add a comment will be better,
A comment:
n2 appearing in the following question means n square, n1/2 appearing in the following question means n square root
please read the following question:
Is positive integer n divisible by 4?
(1) n2 is divisible by 8.
(2) n1/2 is a even integer.
the answer is that each statement alone is sufficient,
I have different idea, I think statement #1 is insufficient, because:
if given n2 = 64, 64 is obviously divisible by 8, and n1/2 = 4√2 ̄, it is not divisible by 4,
if given n2 = 16, 16 can be obviously by 4,
based on these two given examples above, whether statement #1 is sufficient is depending on the value of n2,
thus, I think statement #1 is insufficient.
please help if I made a mistake.
thanks a lot.
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Zoe, when considering S1 on its own, you don't need to consider S2.
That said, if you know that n² = 8 * something, you have
n * n = 2 * 2 * 2 * something
Since each n is the same, each n must have the same number of 2s in it. We can't have one n = 2 and the other n = 2 * 2; then we'd have different values for the same letter!
So each n must = 2 * 2 * (whatever else), and we know n = 4 * something. That might make √n an even integer and it might not, but we don't really care: we've answered what we were asked.("Yes, n IS divisible by 4.")
That said, if you know that n² = 8 * something, you have
n * n = 2 * 2 * 2 * something
Since each n is the same, each n must have the same number of 2s in it. We can't have one n = 2 and the other n = 2 * 2; then we'd have different values for the same letter!
So each n must = 2 * 2 * (whatever else), and we know n = 4 * something. That might make √n an even integer and it might not, but we don't really care: we've answered what we were asked.("Yes, n IS divisible by 4.")
Matt@VeritasPrep wrote:Zoe, when considering S1 on its own, you don't need to consider S2.
Dear Matt,Zoe wrote:if given n2 = 64, 64 is obviously divisible by 8, and n = 4√2 ̄ (here should be n, and I input n1/2 mistakenly ), it is not divisible by 4,
Thanks for your solution.
first, I input n1/2 mistakenly, it should be n = 4√2 ̄
I think I still need your explanation for my given value , n2= 64, n = 4√2 ̄, cannot be divisible by 4,
obviously, here is a value that shows the statement #1 is insufficient.
Please help.
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Yes, and we already know from the original prompt that n must be a positive integer. That removes the possibility where n^2=8, which would satisfy (1) but in that case n would equal 2*(2)^(0.5), which conflicts with the requirement that n be a positive integer.Matt@VeritasPrep wrote:Zoe, when considering S1 on its own, you don't need to consider S2.
That said, if you know that n² = 8 * something, you have
n * n = 2 * 2 * 2 * something
Since each n is the same, each n must have the same number of 2s in it. We can't have one n = 2 and the other n = 2 * 2; then we'd have different values for the same letter!
So each n must = 2 * 2 * (whatever else), and we know n = 4 * something. That might make √n an even integer and it might not, but we don't really care: we've answered what we were asked.("Yes, n IS divisible by 4.")
So I think it's important to note the proof you gave works because n must be an integer. Therefore, n must contain at least two factors of two. If we weren't constrained by that, (1) alone wouldn't be sufficient. Am I correct in that assessment?
800 or bust!
800_or_bust wrote: Yes, and we already know from the original prompt that n must be a positive integer. That removes the possibility where n^2=8, which would satisfy (1) but in that case n would equal 2*(2)^(0.5), which conflicts with the requirement that n be a positive integer.
So I think it's important to note the proof you gave works because n must be an integer. Therefore, n must contain at least two factors of two. If we weren't constrained by that, (1) alone wouldn't be sufficient. Am I correct in that assessment?
Thanks so much.
I got it.
Have a nice day.
>_~
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Yup, this is correct. Since we're told in the prompt that n is an integer, we only need to consider integer solutions, but if we were considering all numbers, we'd have800_or_bust wrote:So I think it's important to note the proof you gave works because n must be an integer. Therefore, n must contain at least two factors of two. If we weren't constrained by that, (1) alone wouldn't be sufficient. Am I correct in that assessment?
n² = 8k, where k is some integer we don't care about
n = 2√(2k)
So if n is an integer, then it's an even integer, but whether it's an integer at all depends on the value of k.
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If n² = 64, then n = 8, so n would be divisible by 4.zoe wrote:Matt@VeritasPrep wrote:Zoe, when considering S1 on its own, you don't need to consider S2.Dear Matt,Zoe wrote:if given n2 = 64, 64 is obviously divisible by 8, and n = 4√2 ̄ (here should be n, and I input n1/2 mistakenly ), it is not divisible by 4,
Thanks for your solution.
first, I input n1/2 mistakenly, it should be n = 4√2 ̄
I think I still need your explanation for my given value , n2= 64, n = 4√2 ̄, cannot be divisible by 4,
obviously, here is a value that shows the statement #1 is insufficient.
Please help.