Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 05 May 2015, 17:12

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# I got this correct through backsolving....but didn't get it

Author Message
TAGS:
Senior Manager
Joined: 18 Jun 2007
Posts: 296
Followers: 2

Kudos [?]: 32 [0], given: 0

I got this correct through backsolving....but didn't get it [#permalink]  09 Feb 2008, 13:47
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
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
Attachment:
New Microsoft Word Document.doc [57 KiB]

 Kaplan Promo Code Knewton GMAT Discount Codes Veritas Prep GMAT Discount Codes
Manager
Joined: 02 Jan 2008
Posts: 159
Followers: 2

Kudos [?]: 69 [0], given: 0

Re: PS: Prep [#permalink]  09 Feb 2008, 13:56
are you solving for v?

btw, you will get v=33 (v^2 = 1089) and answer should be 2.5
Senior Manager
Joined: 18 Jun 2007
Posts: 296
Followers: 2

Kudos [?]: 32 [0], given: 0

Re: PS: Prep [#permalink]  10 Feb 2008, 09:54
yup, I was trying to get the answer through v..I was pretty late last night..got it right in the morning. thx
CEO
Joined: 29 Mar 2007
Posts: 2591
Followers: 16

Kudos [?]: 234 [0], given: 0

Re: PS: Prep [#permalink]  10 Feb 2008, 20:52
rishi2377 wrote:
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
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.
Senior Manager
Joined: 18 Jun 2007
Posts: 296
Followers: 2

Kudos [?]: 32 [0], given: 0

Re: PS: Prep [#permalink]  12 Feb 2008, 06:06
GMATBLACKBELT wrote:
rishi2377 wrote:
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
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.

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.
GMAT Instructor
Joined: 04 Jul 2006
Posts: 1269
Followers: 23

Kudos [?]: 158 [0], given: 0

Re: PS: Prep [#permalink]  12 Feb 2008, 06:13
rishi2377 wrote:
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
Attachment:
New Microsoft Word Document.doc

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
Re: PS: Prep   [#permalink] 12 Feb 2008, 06:13
Similar topics Replies Last post
Similar
Topics:
I asked a question yesterday, but didn't get any satisfactory answer. 2 26 Sep 2014, 11:52
Is the correct answer determined through elimination? I 3 25 Aug 2010, 16:57
Didn't get this one. I was struggled between A and E, and it 1 18 May 2009, 10:50
I was flipping through the Gmat Math Bible and got to the 9 21 Mar 2008, 10:45
Got it correct. But I guess that is largly due to guess. 2 02 Nov 2007, 04:35
Display posts from previous: Sort by