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A rental car agency purchases fleet vehicles in two sizes: a

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A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 02 Dec 2010, 14:14
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A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.
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Re: Car Dealer - Data Sufficiency  [#permalink]

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New post 02 Dec 2010, 17:03
15
7
Yalephd wrote:
A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.

Don't have the OA. I think this is an easy question but I am afraid that it might be deceptively simple. I just want to double check.


This is classic C-trap question. C-trap questions are the questions which are obviously sufficient if we take statements together. When we see such questions we should become very suspicious.

Let # of full-size car be F and # of compact cars be C. Question: C=?

(1) The agency owns 7 total cars --> F+C=7. Clearly insufficient to get C.

(2) The agency paid $66,000 for its cars --> 10,000F+9,000C=66,000 --> 10F+9C=66. Here comes the trap: generally such kind of linear equations (ax+by=c) have infinitely many solutions for x and y, and we cannot get single numerical values for the variables. But since F and C represent # of cars then they must be non-negative integers and in this case 10F+9C=66 is no longer simple linear equation it's Diophantine equation (equations whose solutions must be integers only) and for such kind on equations there might be only one combination of x and y (F and C in out case) possible to satisfy it. When you encounter such kind of problems you must always check by trial and error whether it's the case.

Now, it's quite easy to check whether 10F+9C=66 has one or more solutions. 9C=66-10F so 66 minus multiple of 10 must be multiple of 9: 66 is not a multiple of 9; 56 is not; 46 is not; 36 IS A MULTIPLE OF 9 (F=3 and C=4); 26 is not; 16 is not and 6 is not. So only one combination of F and C satisfies equation 10F+9C=66, namely F=3 and C=4. Sufficient.

Answer: B.

For more on this type of questions check:
eunice-sold-several-cakes-if-each-cake-sold-for-either-109602.html
martha-bought-several-pencils-if-each-pencil-was-either-a-100204.html
a-rental-car-agency-purchases-fleet-vehicles-in-two-sizes-a-105682.html
joe-bought-only-twenty-cent-stamps-and-thirty-cent-stamps-106212.html
a-certain-fruit-stand-sold-apples-for-0-70-each-and-bananas-101966.html
joanna-bought-only-0-15-stamps-and-0-29-stamps-how-many-101743.html
at-an-amusement-park-tom-bought-a-number-of-red-tokens-and-126814.html
collections-confused-need-a-help-81062.html

Hope it helps.
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Re: Car Dealer - Data Sufficiency  [#permalink]

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New post 02 Dec 2010, 17:46
Thank you, Bunuel. I thought it was C. Your explanation was clear as always.

Bunuel wrote:
Yalephd wrote:
A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.

Don't have the OA. I think this is an easy question but I am afraid that it might be deceptively simple. I just want to double check.


This is classic C-trap question. C-trap questions are the questions which are obviously sufficient if we take statements together. When we see such questions we should become very suspicious.

Let # of full-size car be F and # of compact cars be C. Question: C=?

(1) The agency owns 7 total cars --> F+C=7. Clearly insufficient to get C.

(2) The agency paid $66,000 for its cars --> 10,000F+9,000C=66,000 --> 10F+9C=66. Here comes the trap: generally such kind of linear equations (ax+by=c) have infinitely many solutions for x and y, and we can not get single numerical values for the variables. But since F and C represent # of cars then they must be non-negative integers and in this case 10F+9C=66 is no longer simple linear equation it's Diophantine equation (equations whose solutions must be integers only) and for such kind on equations there might be only one combination of x and y (F and C in out case) possible to satisfy it. When you encounter such kind of problems you must always check by trial and error whether it's the case.

Now, it's quite easy to check whether 10F+9C=66 has one or more solutions. 9C=66-10F so 66 minus multiple of 10 must be multiple of 9: 66 is not multiple of 9; 56 is not; 46 is not; 36 IS MULTIPLE OF 9 (F=3 and C=4); 26 is not; 16 is not and 6 is not. So only one combination of F and C satisfies equation 10F+9C=66, namely F=3 and C=4. Sufficient.

Answer: B.

Similar problems: gmat-prep2-92785.html?hilit=linear%20type

Hope it helps.
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Re: Car Dealer - Data Sufficiency  [#permalink]

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New post 02 Dec 2010, 19:46
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1
In my blog post given below, I have discussed in detail how to find integer solutions to linear equations in 2 variables (i.e. equations such as this one)
See if it helps.
http://gmatquant.blogspot.com/2010/11/integral-solutions-of-ax-by-c.html
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 31 May 2013, 05:43
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 31 May 2013, 22:16
1
Yalephd wrote:
A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.


F.S 1 clearly insufficient.

F.S 2 states that 10*f+9*c = 66 [f is the # full size cars;c of compact car]

The only way in which we could get a 6 in the units digit for the RHS is through the factor 9*c --> 9*4 = 36. Thus, the no of compact cars = 4.Sufficient.

B.
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 02 Jun 2013, 14:13
1
Stmt 1 : f + c = 7 …insufficient since we can not determine a specific number



Stmt 2 : 10000f + 9000c = 66000

Dividing both sides by 1000

10f + 9c = 66

Since cars can only be represented by integers, we can set the following equation :

9c = 66 – 10f

C = (66 – 10f)/9

We are looking for a number that is divisible by 9.We need to plug in numbers and arrive at a multiple of 9.

C = (66 – 10*3)/9 = 36/9 = 4

Hence the number of compact cars owned is 4.

Answer : B
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 18 Nov 2013, 11:32
Alt.:

st. 2)



$10.000 $9000 Total
# of cars 7 0 70.000
6 1 69.000
5 2 68.000
4 3 67.000
3 4 66.000 ---> Bingo it matches
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 15 Dec 2017, 08:14
VeritasPrepKarishma wrote:
In my blog post given below, I have discussed in detail how to find integer solutions to linear equations in 2 variables (i.e. equations such as this one)
See if it helps.
http://gmatquant.blogspot.com/2010/11/integral-solutions-of-ax-by-c.html




Your blog posts in comments are always helpful, thankyou.
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 11 Feb 2018, 09:34
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Bunuel wrote:
Bumping for review and further discussion*. Get a kudos point for an alternative solution!

We know that X and Y must be integers and prices are 9.000 or 10.000
Regardless the tens of thousand number, the only way to obtain 6 is if we sold 10-4 cars at 9.000 so we have 4 times 9.000 = 36.000 thus we can determine X which is 3.

So B is sufficient while A is not as said in other posts.

Not sure how clear it is but in my head it goes quicker to do 10-4 = 6 so I need 6 * 9.000 than trying to find for which value we have a multiple of 9
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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 05 Oct 2018, 03:28
Does C trap question like this does really fall under sub-600 level? Bunuel

Bunuel wrote:
Yalephd wrote:
A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.

Don't have the OA. I think this is an easy question but I am afraid that it might be deceptively simple. I just want to double check.


This is classic C-trap question. C-trap questions are the questions which are obviously sufficient if we take statements together. When we see such questions we should become very suspicious.

Let # of full-size car be F and # of compact cars be C. Question: C=?

(1) The agency owns 7 total cars --> F+C=7. Clearly insufficient to get C.

(2) The agency paid $66,000 for its cars --> 10,000F+9,000C=66,000 --> 10F+9C=66. Here comes the trap: generally such kind of linear equations (ax+by=c) have infinitely many solutions for x and y, and we cannot get single numerical values for the variables. But since F and C represent # of cars then they must be non-negative integers and in this case 10F+9C=66 is no longer simple linear equation it's Diophantine equation (equations whose solutions must be integers only) and for such kind on equations there might be only one combination of x and y (F and C in out case) possible to satisfy it. When you encounter such kind of problems you must always check by trial and error whether it's the case.

Now, it's quite easy to check whether 10F+9C=66 has one or more solutions. 9C=66-10F so 66 minus multiple of 10 must be multiple of 9: 66 is not a multiple of 9; 56 is not; 46 is not; 36 IS A MULTIPLE OF 9 (F=3 and C=4); 26 is not; 16 is not and 6 is not. So only one combination of F and C satisfies equation 10F+9C=66, namely F=3 and C=4. Sufficient.

Answer: B.

For more on this type of questions check:
http://gmatclub.com/forum/eunice-sold-s ... 09602.html
http://gmatclub.com/forum/martha-bought ... 00204.html
http://gmatclub.com/forum/a-rental-car- ... 05682.html
http://gmatclub.com/forum/joe-bought-on ... 06212.html
http://gmatclub.com/forum/a-certain-fru ... 01966.html
http://gmatclub.com/forum/joanna-bought ... 01743.html
http://gmatclub.com/forum/at-an-amuseme ... 26814.html
http://gmatclub.com/forum/collections-c ... 81062.html

Hope it helps.

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Re: A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 05 Oct 2018, 05:45
1
parthos wrote:
Does C trap question like this does really fall under sub-600 level? Bunuel

Bunuel wrote:
Yalephd wrote:
A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.

Don't have the OA. I think this is an easy question but I am afraid that it might be deceptively simple. I just want to double check.


This is classic C-trap question. C-trap questions are the questions which are obviously sufficient if we take statements together. When we see such questions we should become very suspicious.

Let # of full-size car be F and # of compact cars be C. Question: C=?

(1) The agency owns 7 total cars --> F+C=7. Clearly insufficient to get C.

(2) The agency paid $66,000 for its cars --> 10,000F+9,000C=66,000 --> 10F+9C=66. Here comes the trap: generally such kind of linear equations (ax+by=c) have infinitely many solutions for x and y, and we cannot get single numerical values for the variables. But since F and C represent # of cars then they must be non-negative integers and in this case 10F+9C=66 is no longer simple linear equation it's Diophantine equation (equations whose solutions must be integers only) and for such kind on equations there might be only one combination of x and y (F and C in out case) possible to satisfy it. When you encounter such kind of problems you must always check by trial and error whether it's the case.

Now, it's quite easy to check whether 10F+9C=66 has one or more solutions. 9C=66-10F so 66 minus multiple of 10 must be multiple of 9: 66 is not a multiple of 9; 56 is not; 46 is not; 36 IS A MULTIPLE OF 9 (F=3 and C=4); 26 is not; 16 is not and 6 is not. So only one combination of F and C satisfies equation 10F+9C=66, namely F=3 and C=4. Sufficient.

Answer: B.

For more on this type of questions check:
http://gmatclub.com/forum/eunice-sold-s ... 09602.html
http://gmatclub.com/forum/martha-bought ... 00204.html
http://gmatclub.com/forum/a-rental-car- ... 05682.html
http://gmatclub.com/forum/joe-bought-on ... 06212.html
http://gmatclub.com/forum/a-certain-fru ... 01966.html
http://gmatclub.com/forum/joanna-bought ... 01743.html
http://gmatclub.com/forum/at-an-amuseme ... 26814.html
http://gmatclub.com/forum/collections-c ... 81062.html

Hope it helps.


The difficulty level of a question is calculated automatically based on the timer stats from the users which attempted the question. So our stats say that it's sub-600 level.
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New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
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A rental car agency purchases fleet vehicles in two sizes: a  [#permalink]

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New post 07 Oct 2018, 03:20
Yalephd wrote:
A rental car agency purchases fleet vehicles in two sizes: a full-size car costs $10,000, and a compact costs $9,000. How many compact cars does the agency own?

(1) The agency owns 7 total cars.

(2) The agency paid $66,000 for its cars.


(1) It could be any combination for the two. INSUFFICIENT

(2) For $66,000, a maximum of 6 full-size cars can be bought but that will leave only $6,000 and a compact car is of $9,000. This cannot be the combination

If 5 full size cars are bought, that leaves $16,000. 1 compact car can be bought and $7,000 This cannot be the combination

If 4 full size cars are bought, that leaves $26,000. 2 compact cars can be bought and $8,000 This cannot be the combination

If 3 full size cars are bought, that leaves $36,000. 4 compact cars can be bought with no remaining amount This is the combination we are looking for

Therefore, B is the answer
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A rental car agency purchases fleet vehicles in two sizes: a &nbs [#permalink] 07 Oct 2018, 03:20
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