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Is a + b > 0 ? [#permalink]
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11 Nov 2015, 01:57
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Is a + b > 0 ? (1) The point (a, b) is in Quadrant II. (2) a  b > 0
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Is a + b > 0 ? [#permalink]
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11 Nov 2015, 02:03
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Re: Is a + b > 0 ? [#permalink]
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11 Nov 2015, 17:26
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Bunuel wrote: Is a + b > 0 ?
(1) The point (a, b) is in Quadrant II.
In this quadrant we have positive x's and negative y's. Hence a > 0 and b < 0. This is not sufficient to say whether a + b > 0. Consider a = 1 and b = 2; and a = 2 and b = 1.
(2) a  b > 0 > a > b. This implies that a is further from 0, on the number line, then b is. Also, not sufficient.
(1)+(2) Since from (1) a > 0 and b < 0, then for (2) we get a  (b) > 0 > a + b > 0. Sufficient.
Answer: C.
Hope it's clear. Hi Bunuel, Please review highlighted part In Statement 1, it says (a,b) in Quadrant II, x should be negative and y should be positive. so a<0 and b>0.



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Re: Is a + b > 0 ? [#permalink]
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11 Nov 2015, 21:06
yeps, x must be negative, y positive but since we need to know the absolute value, A isn't sufficient by itself. C



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Re: Is a + b > 0 ? [#permalink]
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11 Nov 2015, 21:26
shyind wrote: Is a + b > 0 ?
(1) The point (a, b) is in Quadrant II.
(2) a  b > 0 1) statement 1 tells us that a is ive , and b is positive.. But a+b>0 can have an answer NO if lal>lbl or if lal=lbl(in this case answer will be a+b=0) a+b>0 can have an answer YES if lal<lbl .... so insuff.. 2) statement 2 tells us that the absolute value of a is > than that of b.. so if the points are in quadrant l : ans will be YES quadrant ll : ans will be NO quadrant lll : ans will be NO quadrant lV : ans will be YES so insuff combined the answer is only NO.. suff C
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Re: Is a + b > 0 ? [#permalink]
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11 Nov 2015, 22:07
Mo2men wrote: Bunuel wrote: Is a + b > 0 ?
(1) The point (a, b) is in Quadrant II.
In this quadrant we have positive x's and negative y's. Hence a > 0 and b < 0. This is not sufficient to say whether a + b > 0. Consider a = 1 and b = 2; and a = 2 and b = 1.
(2) a  b > 0 > a > b. This implies that a is further from 0, on the number line, then b is. Also, not sufficient.
(1)+(2) Since from (1) a > 0 and b < 0, then for (2) we get a  (b) > 0 > a + b > 0. Sufficient.
Answer: C.
Hope it's clear. Hi Bunuel, Please review highlighted part In Statement 1, it says (a,b) in Quadrant II, x should be negative and y should be positive. so a<0 and b>0. Yes, it's II quadrant ot IV. Edited. Thank you.
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Re: Is a + b > 0 ? [#permalink]
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12 Nov 2015, 04:26
This can be solved by plugging in numbers to prove insufficiency of the statements.
1: (a, b) in Quadrant 2 i.e. a<0 and b>0 for a = 7, b = 3, a+b = 4 <0 for a = 2, b = 3, a+b = 1 > 0 Insufficient as we do not get a definite answer for Is (a+b) <0.
2. a  b >0 for a = 7, b = 3, ab > 0 and a+b = 4 <0 for a = 7, b = 3, ab > 0 however, a+b = 4 > 0 Insufficient as we do not get a definite answer for Is (a+b) <0.
Together, based on statement 1 we know that a is ve and b is +ve. Based on statement 2, we know that absolute value of a is greater than absolute value of b. Therefore, any numbers that we choose that satisfies above condition will result in a+b <0 e.g. (7, 3), (10, 2), etc.
Answer: C. Both statements together are sufficient.
Hope this helps.



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