A bicycle can travel 45 kilometers in 3 hours, and a car can travel 216 kilometers in 4 hours. How much more miles per hour do cars travel on average than bicycles?
自行车3小时行45千米，汽车4小时行216千米．汽车平均每小时比自行车平均每小时多行多少千米？
<gadget id="calculator">216 / 4</gadget>
<output>54</output>

<gadget id="calculator">45 / 3</gadget>
<output>15</output>

<gadget id="calculator">54 - 15</gadget>
<output>39</output>

<result>39</result>