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

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Joined: 31 Jul 2017
Posts: 404
Location: Malaysia
WE: Consulting (Energy and Utilities)
Re: At a speed of 50 miles per hour, a certain car uses 1 gallon of  [#permalink]

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31 Jan 2018, 20:28
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?

Total Distance covered in 5 hours = 250 miles.
1 Gallon consumed every 30 miles. For 250 miles, the total gallon consumbed would be $$\frac{25}{3}$$
Total capacity = 12 Gallon.
Hence, $$25/36$$.
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Joined: 02 Sep 2009
Posts: 48067
Re: At a speed of 50 miles per hour, a certain car uses 1 gallon of  [#permalink]

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31 Jan 2018, 20:59
1
OCDianaOC wrote:
Bunuel 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

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 $$\frac{(\frac{25}{3})}{12} =\frac{25}{36}$$.

I solved the problem with the approach below and got the correct answer. Did I just get lucky? Will this not work on another similar problem?

R x T = D
50mph x 5 hrs = 250 miles

12 gallons x 30 miles = 360 miles (since a car gets 1 gallon of gasoline for every 30 miles).

I then just took 250 miles and divided by 360 miles then reduced down to 25/36.

That's also a correct way to solve the problem.
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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon of  [#permalink]

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13 Aug 2018, 07:57
Top Contributor
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

At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles.
Time = distance/speed
So, time to travel 30 miles = 30/50 = 3/5 hours.
This means that the car uses 1 gallon for every 3/5 hours.

Let x = the number of gallons of gas used during the 5 hour trip.

We get the following equivalent ratios: 1/(3/5) = x/ 5
Cross multiply to get: 5 = (3/5)x
Multiply both sides by 5/3 to get: 25/3 = x
So, the car uses 25/3 gallons of gas

The amount of gasoline used would be what fraction of a full tank?
We get (25/3)/12, which equals 25/36

Cheers,
Brent
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Re: At a speed of 50 miles per hour, a certain car uses 1 gallon of &nbs [#permalink] 13 Aug 2018, 07:57

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