Cars and trucks drive in the same direction from two places 20 kilometers apart at the same time. It is known that a truck travels an average of 50 kilometers per hour, and a car travels 60 kilometers per hour. How many hours after departure can the car catch up with the truck?
轿车和货车同时从相距20千米的两地向同一方向开出．已知货车平均每小时行50千米，轿车每小时行60千米，出发几小时后轿车能追上货车？
<gadget id="calculator">60 - 50</gadget>
<output>10</output>

<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<result>2</result>