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rishi2377
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I got this correct through backsolving....but didn't get it 09 Feb 2008, 14:47
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I got this correct through backsolving....but didn't get it through direct method...
Here is what i tried:

(90/v-3) - (90/v+3) = 0.5
= > {90*(v+3)} - {90*(v-3)}/ v^2 - 3^2 = 0.5

and it is not working :roll:
Attachment:
New Microsoft Word Document.doc



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srp
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I got this correct through backsolving....but didn't get it 09 Feb 2008, 14:56
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are you solving for v?

btw, you will get v=33 (v^2 = 1089) and answer should be 2.5
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rishi2377
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I got this correct through backsolving....but didn't get it 10 Feb 2008, 10:54
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yup, I was trying to get the answer through v..I was pretty late last night..got it right in the morning. thx
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GMATBLACKBELT
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I got this correct through backsolving....but didn't get it 10 Feb 2008, 21:52
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rishi2377
I got this correct through backsolving....but didn't get it through direct method...
Here is what i tried:

(90/v-3) - (90/v+3) = 0.5
= > {90*(v+3)} - {90*(v-3)}/ v^2 - 3^2 = 0.5

and it is not working :roll:
Attachment:
New Microsoft Word Document.doc
Show more

Man this was kindof a nasty lil problem. Easy conceptually, but lots of busy work.

(v-3)(t+1/2)=90
(v+3)(t)=90

vt+v/2-3t-3/2=90
vt+3t

2vt+v-6t=183
-2(vt+3)=90(-2) ---> v=12t+3

(12t+6)(t)=90 ----> t^2+(t/2)^2-15/2=0 ---> (t+3)(t-5/2)=0 so t=2.5

i think a better approach would be to just plug in the answer choices.
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I got this correct through backsolving....but didn't get it 12 Feb 2008, 07:06
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GMATBLACKBELT
rishi2377
I got this correct through backsolving....but didn't get it through direct method...
Here is what i tried:

(90/v-3) - (90/v+3) = 0.5
= > {90*(v+3)} - {90*(v-3)}/ v^2 - 3^2 = 0.5

and it is not working :roll:
Attachment:
New Microsoft Word Document.doc

Man this was kindof a nasty lil problem. Easy conceptually, but lots of busy work.

(v-3)(t+1/2)=90
(v+3)(t)=90

vt+v/2-3t-3/2=90
vt+3t

2vt+v-6t=183
-2(vt+3)=90(-2) ---> v=12t+3

(12t+6)(t)=90 ----> t^2+(t/2)^2-15/2=0 ---> (t+3)(t-5/2)=0 so t=2.5

i think a better approach would be to just plug in the answer choices.
Show more


lol yes black belt...I got it correct through backsolving but tried to get it through direct method and gu6ess what, it was 0315 in the morning. lol thx anyway.
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GRE 1: Q170 V170
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I got this correct through backsolving....but didn't get it 12 Feb 2008, 07:13
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rishi2377
I got this correct through backsolving....but didn't get it through direct method...
Here is what i tried:

(90/v-3) - (90/v+3) = 0.5
= > {90*(v+3)} - {90*(v-3)}/ v^2 - 3^2 = 0.5

and it is not working :roll:
Attachment:
New Microsoft Word Document.doc
Show more


Looks good so far! Rather that factoring to get v^2=1089, we can do the following:
Multiply be 2 to get 180/(v-3) - 180/(v+3) = 1

Look for two factors of 180 = 2^2*3^2*5 that differ by 6: 30 and 36. Thus v=33



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
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