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Re: number properties discrepancy [#permalink]
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IanStewart wrote:
feruz77 wrote:
Here is the first:
The sum of three consecutive even integers is always divisible by which of the following?

I. 2
II. 3
III. 4
IV. 8

A) I and II only
B) I and IV only
C) II and IV only
D) I, II and III only
E) I, II and IV only

OA: D

The solution method is the following:
Sum of three integers = n+n+2+n+4= 3n+6
3n+6 is divisible by 2, 3, 4, but not by 8 for all n=(2,4,6,8...)

(the Source: Winners' Guide to GMAT Math - Part II)


I'm not sure if there's a typo in the question above, or an error in the original source, but the sum of three consecutive even integers is certainly not always divisible by 4. Take 0+2+4, or 4+6+8 for example. Bunuel's solution above is perfect except that he must have thought they were asking about divisibility by 6, not by 4; as the question is written, the answer is A, not D.

The second question you've asked is not worded in a way at all similar to what you'll see on the test (you won't see the word 'thrice' on the GMAT, and the question contains a comma splice).


Sure, they are not asking about 6.
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Re: number properties discrepancy [#permalink]
To: Ian Stewart

You are right because there is not excluded a case with a sum of 0, 2, 4. Then the answer is A. OK.

It seems to me that the first question must be written more pricisely, otherwise one cannot determine whether it is meant only positive consecutive even integers. Without precision word "positive" I have assumed in my first trial of this question that three consecutive even numbers may be in the order -2, 0, 2. In such a case only 0 can satisfy the question, but there is no answer with zero.

Do you agree with my remark?

Do you think that there may such misrepresentation or trick in the official GMAT Test?



Everybody, pls. give your explanations?!
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Re: number properties discrepancy [#permalink]
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feruz77 wrote:
To: Ian Stewart

You are right because there is not excluded a case with a sum of 0, 2, 4. Then the answer is A. OK.

It seems to me that the first question must be written more pricisely, otherwise one cannot determine whether it is meant only positive consecutive even integers. Without precision word "positive" I have assumed in my first trial of this question that three consecutive even numbers may be in the order -2, 0, 2. In such a case only 0 can satisfy the question, but there is no answer with zero.

Do you agree with my remark?

Do you think that there may such misrepresentation or trick in the official GMAT Test?



Everybody, pls. give your explanations?!


I'm not sure understood the red part above.

Anyway, the sum of ANY 3 consecutive even integers is ALWAYS divisible by 2, 3, and 6. If 3 consecutive even integers are -2, 0, and 2 then their sum is 0 and zero is divisible by every integer but zero itself, so it's divisible by 2, 3 and 6 too. So the answer is still A.
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Re: number properties discrepancy [#permalink]
Hi Bunuel,

I got your point, thanks.



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