7. What takes the place now of the constant of proportionality? Where does this number come from? This final graph makes the x-axis easier to follow because it is round numbers instead of decimals. The graph shows a direct relationship between the cost and the number of gallons of gas used to drive 100 miles. This final graph also shows that small increases in mileage for the least fuel efficient vehicles results in large fuel and cost savings (see graph below). For example, going from 1 1 gallons per 100 miles (which corresponds to a mileage of 9 mpg) to 9 gallons per 100 miles (which corresponds to I I mpg) gives large fuel and cost savings ($8). The same 2 mpg increase in fuel efficiency at the higher mileage rates gives smaller and smaller fuel and cost savings. For example, increasing from 26 mpg to 28 mpg corresponds to only saving 0.28 gallons of gas (3.85-3.57 gallons per 100 miles) and saving only $1 on gas costs. Obviously, the best scenario would be to only drive the most fuel efficient vehicles. Yet, small increases in fuel efficiency for the low mileage vehicles can still make a big difference in saving gas and money