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# If in a certain shipment of new cars, the cost of car X is

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Senior Manager
Joined: 30 Aug 2003
Posts: 322
Location: dallas , tx
If in a certain shipment of new cars, the cost of car X is [#permalink]

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10 Dec 2003, 11:07
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If in a certain shipment of new cars, the cost of car X is twice the average of the other 11 cars in the shipment, what fraction of the total cost of 12 cars is the cost of car X?

1/12
1/11
2/13
2/11
1/6
_________________

shubhangi

Director
Joined: 28 Oct 2003
Posts: 501
Location: 55405

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10 Dec 2003, 12:42
easiest to plug. 11 cars at $1000 per. 1 car at$2000.

Total cost, $13000. Cost of expensive car,$2000.

2/13
Director
Joined: 13 Nov 2003
Posts: 960
Location: Florida

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12 Dec 2003, 20:07
assume avg = Y
X=2/11(Y)

X's %age = X/(X+Y)

solve for X..u will get 2/13.
Manager
Joined: 06 Jun 2003
Posts: 59

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12 Dec 2003, 20:39
stoolfi,which kinds of questions do you recommend for using the "plug answer" technique? I start working algebraic solutions instinctively, which is not the most efficient method.
Director
Joined: 28 Oct 2003
Posts: 501
Location: 55405

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12 Dec 2003, 21:20

But since you asked, I almost always try to plug first-- in part because I make too many computation errors the other way.

As you go through the OG, if you time yourself (as you should), make a note of any question that takes longer than 90 seconds and see if you could have done it faster by plugging. This should be especially easy if you can narrow the answers down to two before you start the problem.

Sorry I can't give you a better description.
Manager
Joined: 12 Oct 2003
Posts: 247
Location: USA

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12 Dec 2003, 21:47
I also wanted to know that .. thanks stoolfi .... also, you are being too modest here

maybe we can start a new thread/topic on strategies in solving math probs
CEO
Joined: 15 Aug 2003
Posts: 3454

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12 Dec 2003, 23:54
shubhangi wrote:
If in a certain shipment of new cars, the cost of car X is twice the average of the other 11 cars in the shipment, what fraction of the total cost of 12 cars is the cost of car X?

1/12
1/11
2/13
2/11
1/6

average cost of 11 other cars = C

total cost of 12 cars = 11C + 2C = 13C

Cost of car x =2C

fraction = 2/13
Senior Manager
Joined: 30 Aug 2003
Posts: 322
Location: dallas , tx

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13 Dec 2003, 08:46
Yours is the most easy way Preat...but i was thinking that average means we have to assume X/11..so someting likethat..
Anyways,thanks.
_________________

shubhangi

13 Dec 2003, 08:46
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