shibal wrote:At 50 mph a car uses 1 gallon for every 30 miles. If the car starts with a full tank of 12 gallons and drives for 5 hrs at 50mph, the amount of gas used would be what fraction of the tank?
oa: [spoiler]25/36[/spoiler]
Think of this question as a manipulation of units. Otherwise it is a direct rate/distance question.
5hrs*(50miles)/hr = 250 miles.
now you know the rate of gallons vs miles = 30 miles/gallon.
we want our end result to be in gallons.
so 250miles/(30m/g) = (25/3) gallons.
now they are asking you the fraction of 12 gallon tank used. both units are in gallons.
so (25/3)/12 = 25/36.