Need help on very tough math problem!

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rnschmidt
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Topic: Need help on very tough math problem!
PostMon Nov 20, 2006 6:14 pm
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I just took my first practice test and nailed the verbal (97%) but had some trouble with the math (50%). Here is one of the problems from the old test number 52. Any help is greatly appreciated!

A group of twelve people plan to rent a van and agree to share equally the total cost of the rental, which is E dollars. If n of the people decide not to participate at the last minute, by how many dollars will each remaining person's share of the total cost increase?

A) E/(12-n)

B) (12-n)/E

C) E/[12(12-n)]

D) (nE)/[12(12-n)]

E) [(12-n)E]/(12n)
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jayofbay
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PostTue Nov 21, 2006 4:35 am
Answer is D.
Original amount per person E/12
New amount E/(12-n)

So increase is E/(12-n) - E/12 = (12E - 12E + nE)/12(12-n) = nE/12(12-n)
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chanduveluru
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PostTue Nov 21, 2006 4:47 am
Can you please tell me from where (which sites) you are getting the practice tests. Iam new to this website. thanking you. Chandu

rnschmidt wrote:
I just took my first practice test and nailed the verbal (97%) but had some trouble with the math (50%). Here is one of the problems from the old test number 52. Any help is greatly appreciated!

A group of twelve people plan to rent a van and agree to share equally the total cost of the rental, which is E dollars. If n of the people decide not to participate at the last minute, by how many dollars will each remaining person's share of the total cost increase?

A) E/(12-n)

B) (12-n)/E

C) E/[12(12-n)]

D) (nE)/[12(12-n)]

E) [(12-n)E]/(12n)
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PostTue Nov 21, 2006 9:18 am
chanduveluru wrote:
Can you please tell me from where (which sites) you are getting the practice tests. Iam new to this website. thanking you. Chandu

rnschmidt wrote:
I just took my first practice test and nailed the verbal (97%) but had some trouble with the math (50%). Here is one of the problems from the old test number 52. Any help is greatly appreciated!

A group of twelve people plan to rent a van and agree to share equally the total cost of the rental, which is E dollars. If n of the people decide not to participate at the last minute, by how many dollars will each remaining person's share of the total cost increase?

A) E/(12-n)

B) (12-n)/E

C) E/[12(12-n)]

D) (nE)/[12(12-n)]

E) [(12-n)E]/(12n)
Hi chanduveluru:

Here's a good post to help you: http://www.beatthegmat.com/viewtopic.php?t=758
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Dabolix
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PostFri Dec 15, 2006 1:54 am
I just had a GMAT Prep problem w/ similar concept but harder prob.
Still I'm not quite following your math.
I get up to here:
Original amount per person E/12
New amount E/(12-n)
So increase is E/(12-n) - E/12 =
I don't get how you go from that, to the following:
could you please walk me through it?
(12E - 12E + nE)/12(12-n) = nE/12(12-n)
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mukul
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PostMon Dec 18, 2006 11:26 am
E/(12-n) - E/12 =
I don't get how you go from that, to the following:
could you please walk me through it?
(12E - 12E + nE)/12(12-n) = nE/12(12-n)

Here...I can help...pretty simple...

how wud u get 1/4 -1/5 ??

u will take the lcm of 4 & 5 which will be 4 X 5 = 20
(similarily take lcm here...(12-n) X 12 )
now u will 5 above 4 and 4 above 5...which wil look like
5-4
----
20

rite??

similarily
12XE - (12-n)E
-----------------
(12-n)X12

= 12E-12E+En
--------------
(12-n)X12

and hey ur ans... En/(12-n)12

Hope that helps....quite tricky to explain here...but i tried Smile
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Dabolix
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PostTue Dec 19, 2006 3:04 am
thanks! It's pretty straightforward when you put it like that.
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guynoor
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PostTue Feb 13, 2007 2:53 pm
Dabolix wrote:
I just had a GMAT Prep problem w/ similar concept but harder prob.
Still I'm not quite following your math.
I get up to here:
Original amount per person E/12
New amount E/(12-n)
So increase is E/(12-n) - E/12 =
I don't get how you go from that, to the following:
could you please walk me through it?
(12E - 12E + nE)/12(12-n) = nE/12(12-n)
E/12 GIVES YOU THE COST/PERSON WHEN THERE ARE 12 PEOPLE
E/(12-N) GIVES YOU THE COST/PERSON WHEN THERE ARE 12-N PEOPLE
SO THE DIFFERENCE BETWEEN THE TWO IS THE DIFFERENCE IN THE COST IN THE 2 SCENARIOIS, HENCE

E/(12-N) which will be BIGGER amount due to a SMALLER denom. - E/12 which will be SMALLER number due to a BIGGER denom.

SOLVING

Common Denom. - 12(12-n)

HENCE (12E - 12E + nE)/12(12-n) = nE/12(12-n) [b]

If you have problems doing such questions try to plug in some numbers to actually understand what the author is saying. When you understand the concept behind the question getting to the right answer is just a matter of seconds.

HTH[/b]
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