Drive

https://www.desmos.com/calculator/jxdb9eljxj

Working with a graph of gas consumption against driving speed, we look at the question of the optimal driving speed to minimize the amount of gas used for a fixed trip, or if you like, we minimize litres per kilometer.

We then add a cost for driving time, and that raises the optimal driving speed to a range that seems quite reasonable.

We analyze these problems both graphically and using calculus. For many students, the graphical model found on the first three pages will be of greatest interest.