It will take 4 gallons of gasoline to mow the lawn. Since .5 of the gasoline mows .25 of the lawn you are going to multiply the amount of gasoline by 4, since it is increasing by a rate of .5 to .25.
1/2 gallon = 1/4 lawn
1 gallon = 2/4 lawn
1 1/2 gallons = 3/4 lawn
2 gallons= 4/4 lawn
