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Re: a < 0 < b so compare ab and a+b [#permalink]
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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

Answer: D

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Re: a < 0 < b so compare ab and a+b [#permalink]
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]
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boxing506 wrote:
please add the minus before 1/2 or revise it not to create confusion


Fixed! Sorry about the error.
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Re: a < 0 < b so compare ab and a+b [#permalink]
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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.
the correct answer is D.
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Re: a < 0 < b so compare ab and a+b [#permalink]
D is correct
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Re: a < 0 < b so compare ab and a+b [#permalink]
FatemehAsgarinejad 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.
the correct answer is D.[/b]


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]
*sorry answer "d"
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Re: a < 0 < b so compare ab and a+b [#permalink]
asfandiar wrote:
FatemehAsgarinejad 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.
the correct answer is D.[/b]


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]
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

rx10 GreenlightTestPrep KarunMendiratta sir, Is this always hold true?
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Re: a < 0 < b so compare ab and a+b [#permalink]
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kumarneupane4344 wrote:
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

rx10 GreenlightTestPrep KarunMendiratta sir, Is this always hold true?


For this particular case? Yes
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Re: a < 0 < b so compare ab and a+b [#permalink]
a < 0 < b
This means that a is negative and b is positive

Quantity A = ab

Now, we know that a nd b have opposite sings this means ab < 0
Now, a and b can be any numbers [ can be decimal also]

Let's take two cases
1. a = -1, b = 0.1 => ab = -0.1
2. a = -1, b= 1 => ab= -1

Quantity B = a + b

Lets take the same two cases as above
1. a = -1, b = 0.1 => a + b = -0.9
2. a = -1, b= 1 => a+ b = 0

In case 1 Quantity A > Quantity B
In case 2 Quantity B > Quantity A

So, answer will be D
Hope it helps!
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Re: a < 0 < b so compare ab and a+b [#permalink]
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