Need help on very tough math problem!

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rnschmidt: Newbie | Next Rank: 10 Posts; Posts: 9; Joined: Tue Nov 07, 2006 6:18 am

by rnschmidt » Mon Nov 20, 2006 5:14 pm

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: Junior | Next Rank: 30 Posts; Posts: 25; Joined: Sat Jun 24, 2006 7:01 pm

answer is D

by jayofbay » Tue Nov 21, 2006 3:35 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: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Tue Nov 21, 2006 3:15 am

Re: Need help on very tough math problem!

by chanduveluru » Tue Nov 21, 2006 3:47 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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beatthegmat: Site Admin; Posts: 6778; Joined: Mon Feb 13, 2006 8:30 amFollowed by: 994 members; Location: Los Angeles, CA; Thanked: 1249 times

Re: Need help on very tough math problem!

by beatthegmat » Tue Nov 21, 2006 8:18 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: https://www.beatthegmat.com/viewtopic.php?t=758

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Dabolix: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Thu Dec 14, 2006 9:19 pm

by Dabolix » Fri Dec 15, 2006 12:54 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: Junior | Next Rank: 30 Posts; Posts: 26; Joined: Wed Oct 11, 2006 11:02 pmFollowed by: 8 members; Location: Tuck School of Business, U of Dartmouth; Thanked: 4 times; GMAT Score:770

by mukul » Mon Dec 18, 2006 10:26 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

GMATing: How I made it to an Ivy League B-School!!||How I got a 770!!

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Dabolix: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Thu Dec 14, 2006 9:19 pm

thx

by Dabolix » Tue Dec 19, 2006 2:04 am

thanks! It's pretty straightforward when you put it like that.

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guynoor: Senior | Next Rank: 100 Posts; Posts: 59; Joined: Sat Feb 10, 2007 10:03 pm; Thanked: 1 times

by guynoor » Tue Feb 13, 2007 1:53 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)

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

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BTGmoderatorRO: Moderator; Posts: 772; Joined: Wed Aug 30, 2017 6:29 pmFollowed by: 6 members

by BTGmoderatorRO » Thu Oct 05, 2017 1:39 am

Total cost of renting the van=E
Group of people planning to rent the van=12
Amount of dollars to be share per person=
(Group of people planning to rent the van) / (Amount of dollars to be share per person) = E/12
Number of people that decide not to participate=n
new amount to be share= E/ (12-n)
because of those that decide not to participate, there will be an increase in the amount of dollars to be shared per person
increase= new amount - previous amount shared by 12 people
= E/(12-n) - E/12
we obtain the lowest common multiple (LCM) by multiplying the two denominators to solve this fraction.
LCM= (12-n) * 12
= (12-n)12
note: (12-n) divide through (12-n) and 12 divide 12 in the second fraction.
[(12-n)*12/ (12-n) * E] - [(12-n)*12/ (12) * E] / (12-n)12
[(12E) - (12-n)E ] / (12-n)12
[12E - (12E - nE)] / (12-n)12
12E - 12E + nE) / (12-n)12
:: The remaining person's share of the total cost increases by
nE / (12-n)12
hence, option D is correct

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8153; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

Re: Need help on very tough math problem!

by Scott@TargetTestPrep » Tue Jan 28, 2020 5:09 am

rnschmidt wrote: ↑
Mon Nov 20, 2006 5:14 pm
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)

The old cost per person is E/12. The new cost per person is E/(12 - n). Therefore, the cost increase per person is:

E/(12 - n) - E/12

Getting the common denominator of 12(12 - n), we obtain:

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

Combining the two fractions, we have:

(12E - 12E + nE) / [12(12 - n)]

nE / [12(12 - n)]

Answer: D

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