Are the integers z and f to the right of 0 on the number

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Are the integers z and f to the right of 0 on the number [#permalink]

21 Mar 2012, 12:33

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Question Stats:

83% (01:39) correct

16% (00:53) wrong

based on 12 sessions

Are the integers z and f to the right of 0 on the number line?

(1) The product of z and f is positive.
(2) The sum of z and f is positive.

[Reveal] Spoiler: OA

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Re: Number Line [#permalink]

21 Mar 2012, 12:43

Here is my take:

ZF>0 tells you that z and f have same sign - insuficient because both can be positive or negative

z + f > 0 means either z or f is positive or both are positive so its insufficient

Together sufficient because Z & F have same sign and one is positive so both must be positive

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Re: Are the integers z and f to the right of 0 on the number [#permalink]

21 Mar 2012, 13:11

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Are the integers z and f to the right of 0 on the number line?

Question basically asks whether z and f are both positive.

(1) The product of z and f is positive --> zf>0 --> z and f have the same sign, they are either both positive or both negative. Not sufficient.

(2) The sum of z and f is positive --> z+f>0 --> it's certainly possible that both are positive but it's also possible one to be positive and another negative (for example z=2 and f=-1). Not sufficient.

(1)+(2) Since from (2) z+f>0 then from (1) it's not possible that z and f to be both negative. Hence, z and f are both positive. Sufficient.

Answer: C.
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Re: Are the integers z and f to the right of 0 on the number [#permalink] 21 Mar 2012, 13:11

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Are the integers z and f to the right of 0 on the number

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Are the integers z and f to the right of 0 on the number

Are the integers z and f to the right of 0 on the number

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