Question

A bus goes 400 miles on 25 gallons of gas. How much is the bus's miles per gallon?

Answer 1

Hint:
Divide 400/25

Answer 2

OH! Okay Thankyou!

Answer 3

Better yet is to write it out including the units:

400 miles / 25 gallons = 16 miles / gallon

That serves as a check that you've set the problem up correctly, especially if you have to do some unit conversions along the way. What if the problem wanted to know the mileage in yards/quart?

400 miles / 25 gallons * (1760 yards / 1 mile) * (1 gallon / 4 quarts) = 7040 yards/quart.

Notice how easy it is to fall into the trap of writing out the conversion as 4 quarts/1 gallon, but that gives you units that don't cancel out correctly, which means it is wrong. Because gallons are in the denominator of the fraction, you need them to be in the numerator of the fraction for the conversion.