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If x is a positive number, rounded to the nearest integer, [#permalink]
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14 Feb 2011, 15:44
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If x is a positive number, rounded to the nearest integer, is x^2 equal to 25? (1) x rounded to the nearest integer is 5. (2) x^3 rounded to the nearest integer is 125
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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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16 Feb 2011, 07:37
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1) \(4.5<=x<5.5\)  if we square every object \(~20<=x^2<~30\)  approximately Not sufficient, x^2 could be 20 or 30 or anything between. 2) \(124.5<=x^3<125.5\) Lets check a few numbers 4^2 = 16 4.5^2 = ~20 5^2 = 25 4^3 = 64 4.5^3 = ~94 or so 5^3 = 125 So if x^3 rounded to the nearest integer is 125 then x would need to be very close to 5, like 4.99 or so 2  sufficient.
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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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16 Feb 2011, 09:38
banksy wrote: If x is a positive number, rounded to the nearest integer, is x^2 equal to 25? (1) x rounded to the nearest integer is 5. (2) x^3 rounded to the nearest integer is 125 I am having trouble understanding these statements; x is positive number which is rounded to nearest integer; means x can be 1,2,3,4,5,6,7,... is x^2=25. or is x=5? (1) x rounded to nearest integer is 5; well, if x is already a rounded integer; what does this statement tell us? if it tells us that some real number from 4.5 to 5.4 was rounded to 5 and is treated as x and has value 5. then x=5 and x^2=25. Sufficient. (2) x^3 rounded to nearest integer is 125. Well if x was already a rounded integer as per the question stem, how come it's cube need a rounding. I am lost. Someone please break this down for me.
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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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16 Feb 2011, 09:55
fluke wrote: banksy wrote: If x is a positive number, rounded to the nearest integer, is x^2 equal to 25? (1) x rounded to the nearest integer is 5. (2) x^3 rounded to the nearest integer is 125 I am having trouble understanding these statements; x is positive number which is rounded to nearest integer; means x can be 1,2,3,4,5,6,7,... is x^2=25. or is x=5? (1) x rounded to nearest integer is 5; well, if x is already a rounded integer; what does this statement tell us? if it tells us that some real number from 4.5 to 5.4 was rounded to 5 and is treated as x and has value 5. then x=5 and x^2=25. Sufficient. The question says that x rounded is 5 and asks whether x^2 (where x is not rounded!) is equal to 25 rounded 4.5^2 = ~20.25 which rounds to 20. fluke wrote: banksy wrote: (2) x^3 rounded to nearest integer is 125. Well if x was already a rounded integer as per the question stem, how come it's cube need a rounding.
I am lost.
Someone please break this down for me. The question does not state whether X is an integer or not, x could any number in the range given. x in cube rounded to the nearest integer is 125. x could be 5.001 or 4.995 4.995^3 = 124.625 = rounded to 125
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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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16 Feb 2011, 10:01
Mackieman wrote: fluke wrote: banksy wrote: (2) x^3 rounded to nearest integer is 125. Well if x was already a rounded integer as per the question stem, how come it's cube need a rounding.
I am lost.
Someone please break this down for me. The question does not state whether X is an integer or not, x could any number in the range given. x in cube rounded to the nearest integer is 125. x could be 5.001 or 4.995 4.995^3 = 124.625 = rounded to 125 So; what this statement in the question actually convey: "If x is a positive number, rounded to the nearest integer," Shouldn't it ask; "if x is a +ve number, is x^2 equal to 25?" Why this extra information "rounded to the nearest integer"
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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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16 Feb 2011, 17:12
Mackieman wrote: 1) \(4.5<=x<5.5\)  if we square every object
\(~20<=x^2<~30\)  approximately
Not sufficient, x^2 could be 20 or 30 or anything between.
2) \(124.5<=x^3<125.5\)
Lets check a few numbers 4^2 = 16 4.5^2 = ~20 5^2 = 25
4^3 = 64 4.5^3 = ~94 or so 5^3 = 125
So if x^3 rounded to the nearest integer is 125 then x would need to be very close to 5, like 4.99 or so
2  sufficient. Thanks for the explanation. Need some help though. The question states if x^2 = 25 ? It does not state that if x^2 rounded to the nearest integer = 25. So if X = 4.99 then if x^2 = 24.9 which is not the same as 25. However if X = 5 then x^2 = 25. Hence I think both the statements are not sufficient to provide answer. Please help. Thanks.



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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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17 Feb 2011, 12:52
my only problem is that its not proving its equal to... just somewhere near... is that enough?!?! after all, the question is asking if its equals to...
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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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17 Oct 2014, 23:38
banksy wrote: If x is a positive number, rounded to the nearest integer, is x^2 equal to 25? (1) x rounded to the nearest integer is 5. (2) x^3 rounded to the nearest integer is 125 From statement 2 we infer that x^3 must be in the range 124.5 to 125.5 , anything between this range when rounded will be 125. so we need to know if the cube root of the numbers in the range 124.5 to 125.5 , are such that after taking the cube root , if the numbers obtained are squared , and the squared term rounded , is the rounded squared term = 25 For example Let x^3 = 124.5 cube root of 124.5 =4.99 (4.99)^2= 24.9 24.9 rounded to the nearest integer is 25 So B is sufficient. But my question was how to find the cube root of 124.5 ? )( Above I have used a calculator for this ) any ideas?



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Re: If x is a positive number, rounded to the nearest integer, [#permalink]
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