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# At a speed of 50 miles per hour, a certain car uses 1 gallon

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At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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23 Sep 2010, 14:37
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At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 miles per hour, the amount of gasoline used would be what fraction of a full tank?

A. 3/25
B. 11/36
C. 7/12
D. 2/3
E. 25/36

I am getting 2/3 .Please explain what am i missing?
[Reveal] Spoiler: OA

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At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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23 Sep 2010, 14:39
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At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 miles per hour, the amount of gasoline used would be what fraction of a full tank?

A. 3/25
B. 11/36
C. 7/12
D. 2/3
E. 25/36

In 5 hours at 50 miles per hour car will travel 5*50=250 miles and thus will use 250/30=25/3 gallons of gasoline. Gasoline used/full tank equals to $$\frac{(\frac{25}{3})}{12} =\frac{25}{36}$$.

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24 Sep 2010, 16:04
Gas used = (5 hours)*(50 miles/hour)*(1 gallon/30 miles) = 8+1/3 gallons
Portion used = (8+1/3) / 12 = 25/36

Ans E

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29 Dec 2010, 05:45

At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours. the amount of gasoline used would be what fraction of full tank?

Thank you

KD

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Re: GMAT Pre Q- Query [#permalink]

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29 Dec 2010, 07:53
In the given example SPEED is not mentioned with which the car traveled for 5 hrs with 12 gallons in the tank

Therefore, we have to assume that car traveled with the same speed

Now we can calculate distance traveled by the car in 5 hrs = D = S*t
= 50 * 5 = 250 miles

We know that car travels 30 miles in 1 gallon
Therefore gallons of fuel required for 250 miles = 25/3

Hence, fraction of fuel used = 25 /3*12 = 25 / 36

But according to me something is missed out in the question, because, mostly in GMAT answers are not awkward like this.

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26 Apr 2011, 06:44
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Gasoline used = 250/30 = 25/3

Fraction used = 25/3/12 = 25/36

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30 Apr 2011, 09:32
ans is e

in 5 hours car will travel 250 mile at the rate of 50 miles/hr

then gasoline consumed will be $$250/30= 25/3$$

=> fraction of gasoline used will be (25/3) / 12 === 25/36
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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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30 May 2012, 11:50
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Round off doesn't work.....250/30 is nearly 8.3 gallons..

Now 8.3/12 is not equal to 8/12(which most people who get wrong answer do) or 2/3 which is a trap and hence wrong answer...I fell in the trap,hence i know -:)

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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18 Aug 2013, 19:43
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Speed - 50m/h
Consumption - 1gallon ever 30 miles
Given : 12 gallons of fuel at start
Expected travel on full Tank - 360m/h
Actual Travel : 5 * 50 = 250 m/h

Fraction would be : 250/360 = 25/36

Ans: E

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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18 Sep 2013, 00:38
2 / 3 is trap answer. you dont need to solve beyond 25 / 8 and get ~8. let 25 / 3 remain an then divide by 12 to get 25 / 36

TomB wrote:
At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 miles per hour, the amount of gasoline used would be what fraction of a full tank?

A. 3/25
B. 11/36
C. 7/12
D. 2/3
E. 25/36

I am getting 2/3 .Please explain what am i missing?

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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04 Dec 2016, 03:11
Great Question
Here is what i did in the one =>
At 50 miles/hour

Distance =250miles
so => Used gas => 1/30 *250 => 25/3

Let p be the required fraction.
25/3=p*12
p=25/36

Hence E

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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05 Dec 2016, 07:49
In 5 hrs the car will travel a distance of 250 miles.
1 gallon every 30 miles equates to 25/3 gallons for 250 miles
The amount of gasoline used would be (25/3)/12 = 25/36 gallon

2/3 = 0.6667
25/36 = 0.694
25/3 = 8.3
8.3/12 = 0.691
Hence E is better option than D

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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11 Apr 2017, 13:34
Kind of an extremely long-winded way to answer this question, but it's how I best visualize it is: car travels 30 miles on 1 gallon. Trip total is 250 miles.

250-30=220..first gallon
220-30=210..second gallon
210-30=190..third gallon
190-30=160..fourth gallon
160-30=130..fifth gallon
130-30=100..sixth gallon
100-30=70..seventh gallon
70-30=40..eighth gallon
Left with 10 gallons which = 1/3 gallon

Total of 8.3 gallons over 12 gallon tank. The smallest that can reduce down to is 2/3 so answer choices A,B & C are all out. I then cross-multiplied the remaining two answer choices and got "E". Extremely step-oriented but for me it worked. Clocked-in at under 2 minutes to solve, though.

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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30 May 2017, 17:26
TomB wrote:
At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 miles per hour, the amount of gasoline used would be what fraction of a full tank?

A. 3/25
B. 11/36
C. 7/12
D. 2/3
E. 25/36

I am getting 2/3 .Please explain what am i missing?

1.In 5 hrs the car would have traveled 250 miles.
2. It would have used 250/30 gallons
3. The car started with full tank of 12 gallons
4. Gasoline used as a fraction of full tank is (250/30)/12=25/36
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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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03 Aug 2017, 05:42
I fell for the trap answer as well. I rounded off 8.3/12 which is wrong.

I used the following method to solve this:

Distance= speed x time = 50x5=250 miles

Using ratios,
if 30 miles uses 1 gallon, how many gallons will be needed for 250 gallons?

Gallons needed= 250/30 x 1 = 25/3

Therefore, the answer will be (25/3)/12

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At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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06 Aug 2017, 14:36
It is important to see that all answer choices are in fraction form and hence do any calcs that way.

1 gallon = 30 miles travel

At a speed of 50 miles/hr for 5 hours , total distance travelled d
= $$\frac{50miles}{hr}$$*5hrs
= 250 miles

Total gasoline consumed = $$\frac{250}{30}$$ = $$\frac{25}{3}$$

Total gasoline consumed as part of the total gasoline available
= $$\frac{25}{3}$$*$$\frac{1}{12}$$
= $$\frac{25}{36}$$

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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08 Aug 2017, 03:20
GMAT40 wrote:
Speed - 50m/h
Consumption - 1gallon ever 30 miles
Given : 12 gallons of fuel at start
Expected travel on full Tank - 360m/h
Actual Travel : 5 * 50 = 250 m/h

Fraction would be : 250/360 = 25/36

Ans: E

Thanks a lot! The only option which clarified the last step of dividing by 12. This is the right way of determining the fraction of the done miles vs not done

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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09 Aug 2017, 12:49
TomB wrote:
At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 miles per hour, the amount of gasoline used would be what fraction of a full tank?

A. 3/25
B. 11/36
C. 7/12
D. 2/3
E. 25/36

We are given that a certain car has a rate of 30 miles per gallon if its speed is 50 mph. We are next told that the car starts with a 12-gallon tank and travels for 5 hours at 50 mph.

Since distance = rate x time, we know the car traveled 50 x 5 = 250 miles. We can use the car’s rate and distance traveled to determine how many gallons were used.

Gallons used = distance/rate

Gallons used = 250/30 = 25/3

We need to determine the amount of gasoline used, as a fraction of a full 12-gallon tank.

(25/3)/12 = (25/3) x (1/12) = 25/36

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon [#permalink]

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27 Nov 2017, 16:11
I think I have an easier solution than what has been posted.

We know that 30mpg x 12 gallons in the tank gives us a range of 360 potential miles.

If we are traveling at 50mph for 5 hrs we thus will use 250 potential miles.

250/360 = 25/36

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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon   [#permalink] 27 Nov 2017, 16:11
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