certain army conducts field military training, travels 7.5 kilometers per hour when going there, and arrives in 6 hours. It takes 5 hours to return due to an urgent task. How many kilometers per hour do you travel on average when you return? (Solution by proportional method)
某部队进行野外军事训练，去时每小时行7.5千米，6小时到达．因有紧急任务要5小时返回，回来时平均每小时行多少千米？(用比例方法解)
<gadget id="calculator">7.5 * 6</gadget>
<output>45</output>

<gadget id="calculator">45 / 5</gadget>
<output>9</output>

<result>9</result>