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ds:remainder [#permalink]
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29 Oct 2008, 03:11
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guys
What is the remainder when the positive integer x is divided by 8?
1. when x is divided by 12, the remainder is 5. 2. when x is divided by 18, the remainder is 7.
is it C or E ?
cheers



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Re: ds:remainder [#permalink]
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29 Oct 2008, 03:34
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It will be E.
From stmt1: x = 12a + 5 for a = 0,1,2,3,4,...... From stmt2: x = 18b + 7 for b = 0,1,2,3,......
Combining two, 12a + 5 = 18b + 7, or 12a = 18b + 2 or, 6a = 9b + 1 or, a = (9b+1)/(2*3)
Thus, in order for a to be an integer, 9b+1 should have 2 and 3 as its factors. But, that will never be possible as if any number n has a set of factors, these will not be the factors of (n+1). Accordingly, 9b has 3 as the factor, hence 9b+1 will not have 3 as the factor and accordingly, a will not be an integer.
Hence, even after combining stmt1 and stmt2, we will not get a common number.. Hence, insufficient.



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Re: ds:remainder [#permalink]
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29 Oct 2008, 06:36
scthakur wrote: Thus, in order for a to be an integer, 9b+1 should have 2 and 3 as its factors. But, that will never be possible as if any number n has a set of factors, these will not be the factors of (n+1). Accordingly, 9b has 3 as the factor, hence 9b+1 will not have 3 as the factor and accordingly, a will not be an integer.
Thanks scthakur .... I really never know this property .......... +1!
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Re: ds:remainder [#permalink]
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29 Oct 2008, 09:25
domleon wrote: guys
What is the remainder when the positive integer x is divided by 8?
1. when x is divided by 12, the remainder is 5. 2. when x is divided by 18, the remainder is 7.
is it C or E ?
cheers Seem the question is wrong (or misleading) because any integer, x, when divided by 12 has reminder 5 cannot have reminder 7 when the same integer is divided by 18. the reminder could be 5 or 11 or 17. none can be reminder when x is divided by 18. so this is a flawed question.
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Re: ds:remainder [#permalink]
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29 Oct 2008, 09:42
GMAT TIGER wrote: Seem the question is wrong (or misleading) because any integer, x, when divided by 12 has reminder 5 cannot have reminder 7 when the same integer is divided by 18. the reminder could be 5 or 11 or 17. none can be reminder when x is divided by 18.
so this is a flawed question. Can you explain a bit more I seem to get the point but only partially .....
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Re: ds:remainder [#permalink]
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29 Oct 2008, 13:00
amitdgr wrote: GMAT TIGER wrote: Seem the question is wrong (or misleading) because any integer, x, when divided by 12 has reminder 5 cannot have reminder 7 when the same integer is divided by 18. the reminder could be 5 or 11 or 17. none can be reminder when x is divided by 18.
so this is a flawed question. Can you explain a bit more I seem to get the point but only partially ..... I meant to say X cannot have 2 values. As per the statements 1 and 2, x has 2 values and thats, as per GMAT standard, is substandard. You do not get such questions in real test.
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Re: ds:remainder [#permalink]
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29 Oct 2008, 22:38
GMAT TIGER wrote: domleon wrote: guys
What is the remainder when the positive integer x is divided by 8?
1. when x is divided by 12, the remainder is 5. 2. when x is divided by 18, the remainder is 7.
is it C or E ?
cheers Seem the question is wrong (or misleading) because any integer, x, when divided by 12 has reminder 5 cannot have reminder 7 when the same integer is divided by 18. the reminder could be 5 or 11 or 17. none can be reminder when x is divided by 18. so this is a flawed question. GT, what you say is right only when x is common between stmt1 and stmt2. But, if x is not common between stmt1 and stmt2, then what you say may not be true.



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Re: ds:remainder [#permalink]
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30 Oct 2008, 14:14
scthakur wrote: GMAT TIGER wrote: domleon wrote: guys
What is the remainder when the positive integer x is divided by 8?
1. when x is divided by 12, the remainder is 5. 2. when x is divided by 18, the remainder is 7.
is it C or E ?
cheers Seem the question is wrong (or misleading) because any integer, x, when divided by 12 has reminder 5 cannot have reminder 7 when the same integer is divided by 18. the reminder could be 5 or 11 or 17. none can be reminder when x is divided by 18. so this is a flawed question. GT, what you say is right only when x is common between stmt1 and stmt2. But, if x is not common between stmt1 and stmt2, then what you say may not be true. I said this only in the context of this question. But if x is not common between stmt1 and stmt2, then what I said is also true cuz I have not said anything when the scenerio changes.
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Re: ds:remainder [#permalink]
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30 Oct 2008, 22:36
GMAT TIGER wrote: I said this only in the context of this question. But if x is not common between stmt1 and stmt2, then what I said is also true cuz I have not said anything when the scenerio changes. Well, even in the context of this question, stmt1 gives x = 5,17, 29, ..... stmt2 gives x = 7, 25, 43, ...... and the question is independently giving values of x in statement 1 and in statement 2. Why should the two statements provide a common value (if this is what you meant)?










