Question

Assume you use a revolutionary green car, whose fuel consumption per hour is proportional to the square root the car’ speed. You have to travel 750 km from Windhoek to a village at a constant speed, in a dust storm with a strong headwind of 25 km per hour. Assume that the minimum speed allowed on that road is 20km/h and the maximum speed (due to the storm) is 80 km/h. At what speed should you travel to minimize your fuel consumption. [20]

Answer 1

$$20\le v-25 \le 80$$

$$20+25 \le v \le80+25$$

$$45 \le v \le105$$

Ansver: 45 km/h