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

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Math Expert
Joined: 02 Sep 2009
Posts: 43792
If in a certain shipment of new cars, the cost of car X is twice the [#permalink]

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31 Jan 2018, 23:11
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78% (00:55) correct 22% (01:32) wrong based on 41 sessions

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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 ?

(A) 1/12

(B) 1/11

(C) 2/13

(D) 2/11

(E) 1/6
[Reveal] Spoiler: OA

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If in a certain shipment of new cars, the cost of car X is twice the [#permalink]

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31 Jan 2018, 23:21
Bunuel 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 ?

(A) 1/12

(B) 1/11

(C) 2/13

(D) 2/11

(E) 1/6

Let the average price of the 11 cars be p.
Since, the cost of car X is twice the average, it must be 2p.

Therefore, Car X as a fraction of the total cost of 12 cars is $$\frac{2p}{2p+11p} = \frac{2p}{13p} = \frac{2}{13}$$(Option C)
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If in a certain shipment of new cars, the cost of car X is twice the [#permalink]

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01 Feb 2018, 14:20
Bunuel 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 ?

(A) 1/12

(B) 1/11

(C) 2/13

(D) 2/11

(E) 1/6

Another approach: Assign values

1) Assigned values
Let 11 cars' average cost = $1 Car X cost is twice that average: (2 *$1) = $2 2) Total Cost of 11 cars + Car X? Total cost of 11 cars: A * n = Sum ($1 * 11) = $11 total for all 11 cars Total Cost of all 12 cars = (TC of 11 cars) + (Cost of Car X) Total Cost of 12 cars:$11 + $2 =$13

3) Car X as fraction of total cost?

Fraction: $$\frac{CarXcost}{TotalCost12cars}=\frac{2}{13}=\frac{2}{13}$$

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Re: If in a certain shipment of new cars, the cost of car X is twice the [#permalink]

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02 Feb 2018, 11:21
Bunuel 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 ?

(A) 1/12

(B) 1/11

(C) 2/13

(D) 2/11

(E) 1/6

We can let the average of the 11 cars = n, so the cost of car X is 2n, and thus the total cost of all the cars in the shipment is:

11n + 2n = 13n

Now we can determine what fraction X is of the 12 cars:

2n/13n = 2/13

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Joined: 16 Jan 2018
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If in a certain shipment of new cars, the cost of car X is twice the [#permalink]

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03 Feb 2018, 18:24
Avg of 11 = a
cost of X = 2a
total cost = 13a

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Joined: 06 Sep 2016
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Re: If in a certain shipment of new cars, the cost of car X is twice the [#permalink]

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16 Feb 2018, 06:23
I picked numbers!

Let's assume that all the other 11 cars cost 5€ each
X = 2x5 and the total cost of the other 11 cars would be 55, hence the total cost of the 12 cars will be 55+10 = 65

10/65 --> 2/13, answer choice C
Re: If in a certain shipment of new cars, the cost of car X is twice the   [#permalink] 16 Feb 2018, 06:23
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