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Intern  Joined: 30 Dec 2009
Posts: 10

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Question Stats: 70% (01:41) correct 30% (02:20) wrong based on 25 sessions

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A certain store sells all maps at one price and all books at another price. On Monday the store sold 12 maps and 10 books for a total of $38.00 and on Tuesday the store sold 20 maps and 15 books for a total of$60.00. At this store, how much less does a map sell for than a book?

a. $.25 b.$.50
c. $.75 d.$1.00
e. $1.25 I am brain dead on how to solve this. Thanks! --== Message from the GMAT Club Team ==-- THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION. This discussion does not meet community quality standards. It has been retired. If you would like to discuss this question please re-post it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you. Manager  Joined: 25 Jun 2009 Posts: 231 Re: GMAT paper test...looking for answer [#permalink] Show Tags 1 l02g060 wrote: A certain store sells all maps at one price and all books at another price. On Monday the store sold 12 maps and 10 books for a total of$38.00 and on Tuesday the store sold 20 maps and 15 books for a total of $60.00. At this store, how much less does a map sell for than a book? a.$.25
b. $.50 c.$.75
d. $1.00 e.$1.25

I am brain dead on how to solve this. Thanks!

Lets assume the price of a map = x
and price of the book = y

Now 12x + 10y = 38 = > 6x +5y = 19 -- (a)
20x + 15 y = 60 -- (b)

Multiplying (a) with 3 we get
18x + 15y = 57 -- (c)

Solving these 2 equations ( b and c) we get

x = 1.5
y =2
Manager  Joined: 26 May 2005
Posts: 160
Re: GMAT paper test...looking for answer  [#permalink]

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12m + 10b = 38 (m and b are price of one map and one book respectively)
20m + 15b = 60
b-m?

solving we get m = $1.5, b =$2 and b-m = 0.5

B
Manager  Joined: 01 Feb 2010
Posts: 178
Re: GMAT paper test...looking for answer  [#permalink]

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l02g060 wrote:
A certain store sells all maps at one price and all books at another price. On Monday the store sold 12 maps and 10 books for a total of $38.00 and on Tuesday the store sold 20 maps and 15 books for a total of$60.00. At this store, how much less does a map sell for than a book?

a. $.25 b.$.50
c. $.75 d.$1.00
e. $1.25 I am brain dead on how to solve this. Thanks! Map at rate x books at rate y 12x+10y = 38 20x+15y = 60 solving both x=3/2 = 1.5 y=2 y-x = .5 hence B. Intern  Joined: 30 Dec 2009 Posts: 10 Re: GMAT paper test...looking for answer [#permalink] Show Tags chix475ntu wrote: 12m + 10b = 38 (m and b are price of one map and one book respectively) 20m + 15b = 60 b-m? solving we get m =$1.5, b = $2 and b-m = 0.5 B Do you prefer solving by addition as in prior answer or by substitution? Which works better on more diffuicult question sets? Manager  Joined: 10 Feb 2010 Posts: 133 Re: GMAT paper test...looking for answer [#permalink] Show Tags [quote="l02g060] Do you prefer solving by addition as in prior answer or by substitution? Which works better on more diffuicult question sets?[/quote] Sometimes it is easier to solve than substitute each value. For substitution, it will be helpful if you can eliminate some of the answers choices. Manager  Joined: 26 May 2005 Posts: 160 Re: GMAT paper test...looking for answer [#permalink] Show Tags l02g060 wrote: chix475ntu wrote: 12m + 10b = 38 (m and b are price of one map and one book respectively) 20m + 15b = 60 b-m? solving we get m =$1.5, b = $2 and b-m = 0.5 B Do you prefer solving by addition as in prior answer or by substitution? Which works better on more diffuicult question sets? I usually solve the problem then look at the solution. And also will try to substitute the answer in the equations(more likely for inequalities). If there are only few variables to work with, its will be much faster to solve than to substitute the answers. And for the difficult problems, you need to work on writing the given sentences into equations(once you can do that in a minute, you are good to go ) - rest would be easy to solve. Intern  Joined: 06 Nov 2011 Posts: 34 Location: Germany Concentration: Entrepreneurship, General Management GMAT Date: 03-10-2012 GPA: 3 Re: GMAT paper test...looking for answer [#permalink] Show Tags Got 0.5 Dollar after 2:30 min. Is that a 600points range question or more? Intern  Joined: 24 Feb 2011 Posts: 27 Re: GMAT paper test...looking for answer [#permalink] Show Tags I can get to the 2 equations, but i can't solve them where do you get the x=3/2 ? Manager  Joined: 08 Sep 2011 Posts: 51 Concentration: Finance, Strategy Re: GMAT paper test...looking for answer [#permalink] Show Tags I also got B but it took me a little over 2 mins olivite wrote: I can get to the 2 equations, but i can't solve them where do you get the x=3/2 ? your two equations are (when simplified): 1) 6m+5b=19 2) 4m+3b=12 I'll take the second one and solve for m and you get m=3-(3/4b) plug that into the first equation 6(3-(3/4b))+5b=19 --> 18-(18/4b)+5b=19 --> (-18/4b)+5b=1 ----> 1/2b=1 ---> b=2 now that we know b=2 plug that into either equation 4m+3(2)=12 ---> 4m=6---> m= 3/2 or 1.5 b-m=.5 hope that helps Veritas Prep GMAT Instructor V Joined: 16 Oct 2010 Posts: 9706 Location: Pune, India Re: GMAT paper test...looking for answer [#permalink] Show Tags l02g060 wrote: chix475ntu wrote: 12m + 10b = 38 (m and b are price of one map and one book respectively) 20m + 15b = 60 b-m? solving we get m =$1.5, b = \$2 and b-m = 0.5

B

Do you prefer solving by addition as in prior answer or by substitution? Which works better on more diffuicult question sets?

More often than not, solving the equations simultaneously will give you the answer quickly. Solving by substitution is generally more painful with two equations in two variables.

Bring down your equations to lowest form:

1) 6m+5b=19
2) 4m+3b=12

Now, one way is to multiply the first equation by 3 and the second one by 5. But we see that the calculations involved are a little painful. It can be helpful if you are a little more resourceful with your numbers.

Say, I multiply the second equation by 1.5.
I get: 6m + 4.5b = 18

Now solve them simultaneously:
6m+5b=19
6m + 4.5b = 18

.5b = 1
b = 2
m = 1.5
b-m = .5
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Manager  Joined: 25 May 2011
Posts: 97
Re: GMAT paper test...looking for answer  [#permalink]

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Just solve these 2 equations:

$$6m+5b=19$$
$$4m+3b=12$$

B
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Re: GMAT paper test...looking for answer  [#permalink]

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_________________ Re: GMAT paper test...looking for answer   [#permalink] 30 Oct 2018, 06:11
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