BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

A MGMAT Inequality

Expert replies
Source: — Data Sufficiency |

by liferocks » Mon May 10, 2010 9:40 pm
from 1
|x + 1| = 2|x - 1|

Hence x+1=2x-2 or x+1=2-2x

So x=3 or 1/3...not sufficient

from 2
|x - 3| > 0 ie (x-3)>0 or (x-3)<0
so x<-3 or x>3 ..... sufficient

Ans option B

can you please confirm with OA?
"If you don't know where you are going, any road will get you there."
Lewis Carroll
Join the discussion

by pkw209 » Mon May 10, 2010 9:58 pm
Hey liferocks-

Thanks for the response.

Official answer is actually C

The second statement should be x>3 or x<3 so inefficient. Together, you know that x can't be 3 (based on statement 2) so x=1/3, which is less than 1.

I might be going crazy but what's the rule for absolute value inequality questions?

I usually just take the positive and the negative of the left side of the equation.

i.e., for |x + 1| = 2|x - 1|

--> -(x+1) = 2(x-1) -->-x-1 = 2x-2 -->-3x = -1, x = 1/3

AND

--> x+1 = 2(x-1) -->x=3

Again, I'm probably going crazy but this is right, right?
Join the discussion

by liferocks » Mon May 10, 2010 10:50 pm
pkw209 wrote:Hey liferocks-

Thanks for the response.

Official answer is actually C

The second statement should be x>3 or x<3 so inefficient. Together, you know that x can't be 3 (based on statement 2) so x=1/3, which is less than 1.

I might be going crazy but what's the rule for absolute value inequality questions?

I usually just take the positive and the negative of the left side of the equation.

i.e., for |x + 1| = 2|x - 1|

--> -(x+1) = 2(x-1) -->-x-1 = 2x-2 -->-3x = -1, x = 1/3

AND

--> x+1 = 2(x-1) -->x=3

Again, I'm probably going crazy but this is right, right?
yup..you are absolutely right
"If you don't know where you are going, any road will get you there."
Lewis Carroll
Join the discussion

by gmatmachoman » Mon May 10, 2010 11:04 pm
This is the way I used to work for Inequakities :

st 2 : |x - 3| > 0

case 1 :

x-3 >0

:x>3

Case 2: -(x-3)>0

-x+3>0

-x>-3

Now Multiply using -1 on both sides to remove the negative sign of X.

x<3.

So from above 2 cases, we have x> 3 or x<3. To cross check try some random values plugged into the equation.

ST 1:

U have nicely followed the steps.

Combining st1 & st2, we know that X can't be 3. SO X has to be less than 3. So we have to look out for the value. From St 1 we have X= 1/3.

|1/3| <1. Solved!!
Join the discussion

by pkw209 » Tue May 11, 2010 7:49 am
Thanks guys! :)
Join the discussion