Swallows fly 18.9 kilometers in 0.5 hours, and geese fly 255.5 kilometers in 3.5 hours. How many kilometers per hour do swallows fly less than geese?
燕子0.5小时飞行18.9千米，大雁3.5小时飞行255.5千米．燕子每小时比大雁少飞行多少千米？
<gadget id="calculator">255.5 / 3.5</gadget>
<output>73</output>

<gadget id="calculator">18.9 / 0.5</gadget>
<output>37.8</output>

<gadget id="calculator">73 - 37.8</gadget>
<output>35.2</output>

<result>35.2</result>