Assume that Dave drives at a 30 km/L car X km per year.

Assume that Samantha drives at a 10 km/L car Y km per year.

1) Assume X = Y. If the objective is to minimize the use of gas, should we convince Dave to change to a car with 45 km/L or should we convince Samantha to change to a car with 13 km/L?

2) How does X relate to Y and what would make you impartial about convincing Dave or Samantha to choose the cars in Part 1?

Source: Practice Problems