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If Jake washes x cars in 18 minutes, which of the following expresses

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Bunuel
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If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   17 Jan 2017, 08:04
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If Jake washes x cars in 18 minutes, which of the following expresses the number of minutes it would take him to wash 3x + 3 cars?

A. 6x + 3
B. 54x + x/6
C. 54(x + 1)/x
D. (x + 1)/6
E. 54 + (x + 1)/2
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C
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LarryM
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   17 Jan 2017, 08:21
Answer is C.
X cars in 18 mins hence 3X cars in 3*18=54 mins

X cars in 18 mins implies 1 car in 18/x mins and thus 3 cars in 54/x mins
thus 3X+3=54(1+1/x)
on simplification =54(x+1)/x
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   17 Jan 2017, 11:06
Bunuel wrote:
If Jake washes x cars in 18 minutes, which of the following expresses the number of minutes it would take him to wash 3x + 3 cars?

A. 6x + 3
B. 54x + x/6
C. 54(x + 1)/x
D. (x + 1)/6
E. 54 + (x + 1)/2



Lets say Jake washes 9 (x=9) cars in 18 minutes. then he takes 2 min per car. So for 3x+3 cars, ie, 3*9+3 = 30 cars, he will take 60 min.
Now look at the options, see which will give the value 60 if x = 9.
Hence, C.
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   17 Jan 2017, 11:27
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We can express the original ratio R as \(\frac{x}{18}\)
To find the time to wash 3x + 3 cars we can divide the new amount by the original ratio. \(\frac{3x + 3}{(x/18)}\)
Correct answer is C
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   18 Jan 2017, 06:26
Let x =18 cars

Work =Rate * Time

18 =Rate * 18.......Rate= 1 car/min

To finish (3x + 3) cars , it means washing up 57 cars.

Time = 57/1 = 57 min.

Applying in each answer choice:


A. 6x + 3.........No need to calculate as 6 *18 is GREATER than 57........Eliminate

B. 54x + x/6........Same like A.......Eliminate

C. 54(x + 1)/x .......54 *19/18 = 3 *19 = 57 ...........our Target

D. (x + 1)/6...........Very low..................Eliminate

E. 54 + (x + 1)/2..........54+9 GREATER tan required ......Eliminate

Answer: C
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   23 Jan 2017, 07:13
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Bunuel wrote:
If Jake washes x cars in 18 minutes, which of the following expresses the number of minutes it would take him to wash 3x + 3 cars?

A. 6x + 3
B. 54x + x/6
C. 54(x + 1)/x
D. (x + 1)/6
E. 54 + (x + 1)/2


We can set up a simple proportion in which n = the number of minutes it takes Jake to wash 3x + 3 cars.

x/18 = (3x + 3)/n

nx = 18(3x + 3)

nx = 54x + 54

nx = 54(x + 1)

n = 54(x + 1)/x

Answer: C
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink] New post   07 Jun 2021, 05:19
LarryM wrote:
Answer is C.
X cars in 18 mins hence 3X cars in 3*18=54 mins

X cars in 18 mins implies 1 car in 18/x mins and thus 3 cars in 54/x mins
thus 3X+3=54(1+1/x)
on simplification =54(x+1)/x


Could you explain how you came to this finding: X cars in 18 mins implies 1 car in 18/x mins and thus 3 cars in 54/x mins
thus 3X+3=54(1+1/x)

I cannot figure it out
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Re: If Jake washes x cars in 18 minutes, which of the following expresses [#permalink]
07 Jun 2021, 05:19
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