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Inequality OG 11 Diagnostic DS 33 Confused!

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Inequality OG 11 Diagnostic DS 33 Confused!

by sabal » Tue Nov 18, 2008 10:34 pm
I have my GMAT tomorrow ie 20th of Nov 08
This Question is from OG11 Diagnostic 33
Got a lil confused with this question

Q. Is 5^(x+2)/25<1?
1. 5^x <1
2. x<0

The OA is D
I solved the inequality in the question like this
=5^(x+2)<1*25
=5^(x+2)<25
=5^(x+2)<5^2 (cancelling out 5 from both sides)
=(x+2)<2
Therefore, x<0 (same as statement 2)

Another Way,
=5^(x+2)/5^2<1
=5^x*5^2/5^2<1
=5^x<1 (Substituting, 5^0=1)(same as Statement1!)
=5^x<5^0 (cancelling out 5 from both sides)
Therefore, x<0 (same as statement 2)

What is wrong in the way i solved it?
Is the way I solved this inequality wrong??
(The cancelling ou the base bit??)
have I got the DS logic wrong the last minute?
So if someone can just explain me this DS inequality, would be very happy!!!
Last edited by sabal on Tue Nov 18, 2008 11:35 pm, edited 1 time in total.
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Source: — Data Sufficiency |
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by vishubn » Tue Nov 18, 2008 11:11 pm
=5^(x+2)/5^2<1
=5^x*5^2/5^2<1
=5^x<1 (Substituting, 5^0=1)
=5^x<5^0 (cancelling out 5 from both sides)
Therefore, x<1
why did u get 5^x<5^0 as x<1

it should be x<0 right !! i am sure this mgith due to the stress :)

ANd all the best !!!

Vishu
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by sabal » Wed Nov 19, 2008 12:24 am
Corrected that error
Is the way I simplified that Inequality correct?
Just wanted to know the basis for the correct answer.
cuz the equation in the question itself gives us the Statements 1 and 2

Just need some clarification.
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by vishubn » Wed Nov 19, 2008 1:22 am
Just wanted to know the basis for the correct answer.
cuz the equation in the question itself gives us the Statements 1 and 2
ya i think i would done wither of the approach !! I dont see anythign wrong ??

Do u want to solve and rill down to the OA???

Vishu
p.s. i presume u know how to solve and asking for option to solve
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by sabal » Wed Nov 19, 2008 1:40 am
I understood what was wrong!
On reading the question carefully.... "IS"....??
We assumed that the question inequality is TRUE. this is a wrong approach!!!
This is the Yes/ No type Question.
The question is asking if it is true?
The question does not say that the 5^(x+2)/25 <1 is True.

So A and B both satisfy the condition thus making the inequality true!!
Therefore the answer is D.


Thanks a lot anyway!!!
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by jimmiejaz » Wed Nov 19, 2008 5:12 am
First of all best of luck for your exam.

I would like to point one thing that might save you time.
As i look at your explanation, when you reach at 5^x<1 and that is what is given in the first statement please STOP at that point and move to the next statement. If you solve a D>S question and get to a point which is given in one of the statements, then that statement is SUFFICIENT.
It will save you time.
Everything else is fine!!! :)
Good luck :D
What if i have not yet beat the beast, I know i will beat it!!!!!!!!
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Re: Inequality OG 11 Diagnostic DS 33 Confused!

by vittalgmat » Wed Nov 19, 2008 3:35 pm
sabal wrote:I have my GMAT tomorrow ie 20th of Nov 08
This Question is from OG11 Diagnostic 33
Got a lil confused with this question

Q. Is 5^(x+2)/25<1?
1. 5^x <1
2. x<0

The OA is D
I solved the inequality in the question like this
=5^(x+2)<1*25
=5^(x+2)<25
=5^(x+2)<5^2 (cancelling out 5 from both sides)
=(x+2)<2
Therefore, x<0 (same as statement 2)

Another Way,
=5^(x+2)/5^2<1
=5^x*5^2/5^2<1
=5^x<1 (Substituting, 5^0=1)(same as Statement1!)
=5^x<5^0 (cancelling out 5 from both sides)
Therefore, x<0 (same as statement 2)

What is wrong in the way i solved it?
Is the way I solved this inequality wrong??
(The cancelling ou the base bit??)
have I got the DS logic wrong the last minute?
So if someone can just explain me this DS inequality, would be very happy!!!
All the best Sabal.
Crack this 800 barrier !!!!!
-V
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by cramya » Wed Nov 19, 2008 8:14 pm
First of all wish u the very best of luck! We all hope u do well on the GMAT.


The question stem itself can be simplified

5^(x+2) / 25 = 5^ x * 5 ^2 / 25 = 5^x * 25/25

So the question boils down to

Is 5^x<1

Stmt I

Exactly what we want is given

SUFF

Stmt II

x<0

We know any integer raised to a neagtive exponent will always be less than 1

SUFF

D)
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