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# GRE Math Challenge #87- Which of the following CANNOT

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GRE Math Challenge #87- Which of the following CANNOT [#permalink]  09 May 2015, 11:35
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Question Stats:

83% (01:32) correct 16% (00:01) wrong based on 6 sessions
Which of the following CANNOT be the sum of two integers that have a product of 30?

(A) 31
(B) 17
(C) –11
(D) –13
(E) –21
[Reveal] Spoiler: OA

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Sandy
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Re: GRE Math Challenge #87- Which of the following CANNOT [#permalink]  18 Dec 2017, 00:45
sandy wrote:
Which of the following CANNOT be the sum of two integers that have a product of 30?

(A) 31
(B) 17
(C) –11
(D) –13
(E) –21

Here 30 can be written as-

5 * 6

10 * 3

15 * 2

The sum of these integeres are

5 +6 = 11

10 + 3 =13

15 + 2 = 17

But sum of these can also be negative, since negative * negative = postive i. e

-5 + (-6) = -11 and -5 * -6 = 30

-10 + (-3)= -13 and -10 * -3 = 30

-15 + (-2)= -17 and -15 * -2 = 30.

Thus only -21 donot fit into this and hence is the answer
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Re: GRE Math Challenge #87- Which of the following CANNOT [#permalink]  18 Dec 2017, 02:33
We can list the factors of 30.
30 * 1 = 30 SUM = 31
15 * 2 = 30 SUM = 17
10 * 3 = 30 SUM = 13
6 * 5 = 30 SUM = 11

Remember that two negative numbers give us a positive number. So we shoukd consider their negatives.
The only answer that does not show up us D.
Re: GRE Math Challenge #87- Which of the following CANNOT   [#permalink] 18 Dec 2017, 02:33
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# GRE Math Challenge #87- Which of the following CANNOT

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