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Re: If [x] denotes the least integer greater than or equal to x
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09 Jun 2013, 12:53
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I got the right answer but the question is tricky for me: "if [x] denotes the least integer greater than or equal to x"... does it concern only numbers like [1.5]=2; [-1.5]=-1;... or [1.4] will also be rounded to 2?
Re: If [x] denotes the least integer greater than or equal to x
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09 Jun 2013, 12:57
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6
ED1290 wrote:
I got the right answer but the question is tricky for me: "if [x] denotes the least integer greater than or equal to x"... does it concern only numbers like [1.5]=2; [-1.5]=-1;... or [1.4] will also be rounded to 2?
Re: If [x] denotes the least integer greater than or equal to x
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07 Oct 2015, 20:59
Hi everyone... This may sound strange but this is the first question I have ever come across [] to denote rounding up. I mistakenly treated it as || (absolute value) so obviously got the question wrong... Can I just confirm that this is a standard type of mathematical notation that is used on the GMAT? I have not seen this anywhere....
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"[x] denotes to be the least integer no less than x" i can see why this is rounding down
but "If [x] is the greatest integer less than or equal to x"i dont see how thisis rounding down and why
"[x] denotes the least integer greater than or equal to x" why is this rounding up... i mean if theres only 2 of these i guess i could memorise but i'm trying to understand why...
please help. Ive been stuck on this interpretation for ages i dont want to just memorise it.
"[x] denotes to be the least integer no less than x" i can see why this is rounding down
but "If [x] is the greatest integer less than or equal to x"i dont see how thisis rounding down and why
"[x] denotes the least integer greater than or equal to x" why is this rounding up... i mean if theres only 2 of these i guess i could memorise but i'm trying to understand why...
please help. Ive been stuck on this interpretation for ages i dont want to just memorise it.
A quick comment. DO NOT memorize these definitions as they are not fixed. GMAT can change the definition of what the [x] does. Just try to understand what is the given definition.
Try to break it down in manageable chunks.
Case 1: "If [x] is the greatest integer less than or equal to x" ---> let x=4.4 what is the greatest integer LESS THAN or EQUAL to x ? Answer is 4 (5 will be GREATER THAN and NOT less than).You will get the equality when x = integer.
Thus, based on the definition of [x] above, [4.4] = 4 (you rounded DOWN ---> you went to a lower number).
Case 2: "[x] denotes the least integer greater than or equal to x" ---> let x =4.4 ---> based on this current definition, what is the LEAST integer GREATER or EQUAL to x? Answer is 5 (4 will not be correct here as 4<4.4). You will get the equality when x = integer.
Thus, based on the definition of [x] above, [4.4] = 5 (you rounded UP ---> you went to a higher number).
Do not memorize functional definitions as these definitions can change. Example, I can give you a question telling you that [x] denotes a function such that [x] =\(x^2\) etc.
"[x] denotes to be the least integer no less than x" i can see why this is rounding down
but "If [x] is the greatest integer less than or equal to x"i dont see how thisis rounding down and why
"[x] denotes the least integer greater than or equal to x" why is this rounding up... i mean if theres only 2 of these i guess i could memorise but i'm trying to understand why...
please help. Ive been stuck on this interpretation for ages i dont want to just memorise it.
A quick comment. DO NOT memorize these definitions as they are not fixed. GMAT can change the definition of what the [x] does. Just try to understand what is the given definition.
Try to break it down in manageable chunks.
Case 1: "If [x] is the greatest integer less than or equal to x" ---> let x=4.4 what is the greatest integer LESS THAN or EQUAL to x ? Answer is 4 (5 will be GREATER THAN and NOT less than).You will get the equality when x = integer.
Thus, based on the definition of [x] above, [4.4] = 4 (you rounded DOWN ---> you went to a lower number).
Case 2: "[x] denotes the least integer greater than or equal to x" ---> let x =4.4 ---> based on this current definition, what is the LEAST integer GREATER or EQUAL to x? Answer is 5 (4 will not be correct here as 4<4.4). You will get the equality when x = integer.
Thus, based on the definition of [x] above, [4.4] = 5 (you rounded UP ---> you went to a higher number).
Do not memorize functional definitions as these definitions can change. Example, I can give you a question telling you that [x] denotes a function such that [x] =\(x^2\) etc.
Hope this helps.
Thanks for the explanation and time explain it to me. I thnk i understand it. I agree i should not memorise it. Thats why i was looking for an explanation.
Re: If [x] denotes the least integer greater than or equal to x
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13 Jan 2017, 06:26
Hi,
Please note that greatest integer and least integer have two separate standard symbols, and GMAT is not going to use one symbol for another. Please refer the question no 111(DS) and 178(PS) OG 16th edition.
Two symbols are as follows:
\(\lceil x \rceil\): least integer greater than or equal to x.
If [x] denotes the least integer greater than or equal to x
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19 Jun 2017, 01:48
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chesstitans wrote:
How to deal with such kind of gmat question in a general way?
Hi,
I think the point here is to understand the phrase "the least integer greater than or equal to x". It means that if we have a number x, then just round it up to the possible smallest integer and we will get [x]. Remember that x could be anything, not just an integer. For example, if x=-1.2, then [x]=-1. Or if x=5, then [x]=5.
This is a DS question. Then we read the information given in each statement and put it into number line to figure out whether we could answer the question.
For example, (1) -1<x<1 Put -1 and 1 into the number line. We'll see that there are many situations to test. If -1<x=<0, then [x]=0. But that will not be necessarily the case, if 0<x<1. Because if 0<x<1, then [x]=1. Inconsistent answers mean insufficient statement.
Re: If [x] denotes the least integer greater than or equal to x
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27 Feb 2019, 07:26
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macwanjason wrote:
If [x] denotes the least integer greater than or equal to x, is [x] = 0?
(1) -1< x< 1 (2) x < 0
Target question:Is [x] = 0? This is a good candidate for rephrasing the target question.
Given: [x] denotes the least integer greater than or equal to x
Let's make sure we understand what this [] symbol means. Here are a few examples: [3.1] = 4 [5.8] = 6 [0.7] = 1 [-0.9] = 0 [0] = 0 [-4.6] = -4
We can see that [x] = 0, when -1 ≤ x < 0 So, we can REPHRASE the target question . . .
REPHRASED target question:Is -1 ≤ x < 0 ?
Aside: My video below has tips on rephrasing the target question
Statement 1: -1< x< 1 Let's TEST some values. There are several values of x that satisfy statement 1. Here are two: Case a: x = -0.5. In this case, the answer to the REPHRASED target question is YES, it IS the case that -1 ≤ x < 0 Case b: x = 0.5. In this case, the answer to the REPHRASED target question is NO, it is NOT the case that -1 ≤ x < 0 Since we cannot answer the REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: x < 0 Let's TEST some values. There are several values of x that satisfy statement 2. Here are two: Case a: x = -0.5. In this case, the answer to the REPHRASED target question is YES, it IS the case that -1 ≤ x < 0 Case b: x = -3. In this case, the answer to the REPHRASED target question is NO, it is NOT the case that -1 ≤ x < 0 Since we cannot answer the REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined When we combine the two statements, we get the inequality -1 < x < 0 So, for ALL possible values of x, the answer to the REPHRASED target question is YES, it IS the case that -1 ≤ x < 0 Since we can answer the REPHRASED target question with certainty, the combined statements are SUFFICIENT