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Absolute Values

by kumard24 » Sun Mar 30, 2008 6:44 am
Is |a| > |b|?

(1) b < -a

(2) a < 0

This question has baffled me! In the answer it states......we can rephrase this question as: "Is a farther away from zero than b, on the number-line?" We can solve this question by picking numbers:

Just dont get this statement
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hm

by resilient » Sun Mar 30, 2008 8:14 am
whats source? qa please
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by Kaunteya1 » Sun Mar 30, 2008 10:35 am
From statement one:

1) b<-a

This means that b is negative smaller than one. a is closer to zero on the number line, and b is further away if b<-a. Therefore the absolute value of b will be greater than a and you can answer NO to statement 1.

2) just tell you that a is a negative number but does not tell you anything about b.

I would choose A.

I hope that is correnct.
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by Kaunteya1 » Sun Mar 30, 2008 10:37 am
From statement one:

1) b<-a

This means that b is negative smaller than one. a is closer to zero on the number line, and b is further away if b<-a. Therefore the absolute value of b will be greater than a and you can answer NO to statement 1.

2) just tell you that a is a negative number but does not tell you anything about b.

I would choose A.

I hope that is correnct.
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testing numbers

by resilient » Sun Mar 30, 2008 11:10 am
statement 1: b<-a

lets pick some numbers to solidify thoughts.
----b------a--------plug in and test to see answer.
1 -2 yes
-2 -2 no
2 3 yes



statement 2: need b so insufficient

together: testing numbers again with both constraints from st. 1 and st.2
----b--------a-------plug in and test to see answer
1 -2 yes
-2 -2 no


qa is E.










remember we are plugging in a neg number which turn into positive (statement 1)
I wonder what level question this is.
PLEASE POST QA AND SOURCE PLEASE!
I hope this makes sense to you guys. I hope Im right too. lol
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Re: Absolute Values

by Stuart@KaplanGMAT » Sun Mar 30, 2008 9:22 pm
kumard24 wrote:Is |a| > |b|?

(1) b < -a

(2) a < 0
(1) b < -a

Let's pick some numbers that fit this rule and see if we can get a yes and a no answer.

b = -50, a = 3 (-50 < -3, so valid numbers). Is |3| > |-50|? No.

b = -50, a = -100 (-50 < -(-100), so valid numbers. Is |-100| > |-50|? Yes.

We can get a no and a yes - insufficient.

(2) a < 0. No info about (b), so insufficient.

Combined:

Now we have to pick numbers that follow BOTH rules.

We're no longer allowed to pick b=-50 and a=3 (since now a<0), but we can still pick b=-50 and a=-100: that's a yes answer.

We could also pick:

b = -50 and a = -3 (-50 < -(-3) and -3 < 0, so valid numbers). Is |-3| > |-50|? No!

So, we can still get both a yes and a no - insufficient: choose (e).
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stuart

by resilient » Sun Mar 30, 2008 9:52 pm
Stuart do i have the underlying reasoning right!
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Re: stuart

by Stuart@KaplanGMAT » Mon Mar 31, 2008 8:32 am
Enginpasa1 wrote:Stuart do i have the underlying reasoning right!
You chose all valid numbers, so it looks like you're on the right track!
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