4. 202 City A has 157 tons of goods to be transported to City B. The load capacity of a large truck is 5 tons, and that of a small truck is 2 tons. The fuel consumption of a large truck is 20 liters, and that of a small truck is 10 liters. How many large trucks and small trucks should be used to minimize fuel consumption?
[Solution] The fuel consumption for transporting goods with a large truck is 4 liters/ton, and for a small truck, it is 5 liters/ton. Therefore, to minimize fuel consumption, we must use the large truck as much as possible.
157 divided by 5 gives a quotient of 31 and a remainder of 2, so we use 31 large trucks and 1 small truck to transport the goods, which results in the least fuel consumption.