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# a < 0 < b so compare ab and a+b

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a < 0 < b so compare ab and a+b [#permalink]  27 Oct 2016, 12:44
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57% (00:44) correct 42% (00:41) wrong based on 68 sessions
a < 0 < b

 Quantity A Quantity B ab a+b

A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.

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[Reveal] Spoiler: OA

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Re: a < 0 < b so compare ab and a+b [#permalink]  27 Oct 2016, 12:47
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Explanation

Plug in values for a and b. If a = −2 and b = 2, then Quantity B is greater. Eliminate choices A and C. If $$a=\frac{-1}{2}$$ and $$b = \frac{1}{4}$$, then Quantity A is greater. Eliminate choice B.

Hence option D is correct.
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Re: a < 0 < b so compare ab and a+b [#permalink]  21 Jul 2017, 02:47
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I think the explanation is not properly written. Here it is given that a<0<b, then how can we assume the value of a as 1/2?
if we take a=-1 and b=1, then Column B is greater. Again if we take a=-1 and b=1/2, then both the columns are equal, i.e, Column C
So the answer will be D.
Plz verify if possible
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Re: a < 0 < b so compare ab and a+b [#permalink]  24 Jul 2017, 14:37
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sandy wrote:
a < 0 < b

 Quantity A Quantity B ab a+b

Given: a < 0 < b
So, a is NEGATIVE and b is POSITIVE

Let's test some values of a and b that satisfy the given information.

Let's first try a = -1 and b = 1
We get:
Quantity A: ab = (-1)(1) = -1
Quantity B: a+b = (-1) + 1 = 0
In this case, Quantity B is greater

Now try a = -2 and b = 0.5
We get:
Quantity A: ab = (-2)(0.5) = -1
Quantity B: a+b = (-2) + 0.5 = -1.5
In this case, Quantity A is greater

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Re: a < 0 < b so compare ab and a+b [#permalink]  07 Mar 2018, 04:36
sandy wrote:
Explanation

Plug in values for a and b. If a = −2 and b = 2, then Quantity B is greater. Eliminate choices A and C. If $$\frac{1}{2}$$ and b = $$\frac{1}{4}$$, then Quantity A is greater. Eliminate choice B.

Hence option D is correct.

please add the minus before 1/2 or revise it not to create confusion
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Re: a < 0 < b so compare ab and a+b [#permalink]  07 Mar 2018, 15:56
Expert's post
boxing506 wrote:
please add the minus before 1/2 or revise it not to create confusion

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Re: a < 0 < b so compare ab and a+b [#permalink]  07 Mar 2018, 20:10
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correct: D
a < 0 < b
for comparing ab and a+b we can't do any simplifications.
we know a is negative and b is positive.Thus, ab is always a negative value. but depending on the value of a and b, a+b can be either positive or negative.
if |a| > |b| : ab is always negative and a+b is negative, so A > B
if |a| <|b| : ab is always negative and a+b is positive, so A < B
if |a| = |b| : ab is always negative and a+b equals zero, so A < B
so based on the relationship between a and b and information, we can't figure out which one is less or more.

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Re: a < 0 < b so compare ab and a+b [#permalink]  12 Mar 2018, 01:26
D is correct
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Re: a < 0 < b so compare ab and a+b [#permalink]  03 Dec 2018, 04:44
correct: D
a < 0 < b
[b]for comparing ab and a+b we can't do any simplifications.

we know a is negative and b is positive.Thus, ab is always a negative value. but depending on the value of a and b, a+b can be either positive or negative.
if |a| > |b| : ab is always negative and a+b is negative, so A > B
if |a| <|b| : ab is always negative and a+b is positive, so A < B
if |a| = |b| : ab is always negative and a+b equals zero, so A < B
so based on the relationship between a and b and information, we can't figure out which one is less or more.

Hi,

Fatima, refering to the highlighted part. I think we can simplify QTY A & B since B>0. We can divide b on both sides. It's a quesiton. I simplified it to get the answer b.
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Re: a < 0 < b so compare ab and a+b [#permalink]  03 Dec 2018, 04:44
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Re: a < 0 < b so compare ab and a+b [#permalink]  03 Dec 2018, 14:31
asfandiar wrote:
correct: D
a < 0 < b
[b]for comparing ab and a+b we can't do any simplifications.

we know a is negative and b is positive.Thus, ab is always a negative value. but depending on the value of a and b, a+b can be either positive or negative.
if |a| > |b| : ab is always negative and a+b is negative, so A > B
if |a| <|b| : ab is always negative and a+b is positive, so A < B
if |a| = |b| : ab is always negative and a+b equals zero, so A < B
so based on the relationship between a and b and information, we can't figure out which one is less or more.

Hi,

Fatima, refering to the highlighted part. I think we can simplify QTY A & B since B>0. We can divide b on both sides. It's a quesiton. I simplified it to get the answer b.

Hello,
By simplification I meant conversion between parameters of ab and a+b, for instance, if we had ab and a(b+1) we could.
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Re: a < 0 < b so compare ab and a+b   [#permalink] 03 Dec 2018, 14:31
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