A truck transports goods from A to B, travels 50 kilometers per hour, and arrives in 3.2 hours. It takes 0.7 hours less to return to A with an empty truck. How many kilometers per hour does the truck return to A on average?
一辆卡车从甲地运输货物到乙地，每小时行50千米，3.2小时到达．空车返回甲地时少用了0.7小时，卡车返回甲地平均每小时行多少千米？
<gadget id="calculator">3.2 - 0.7</gadget>
<output>2.5</output>

<gadget id="calculator">3.2 / 2.5</gadget>
<output>1.28</output>

<gadget id="calculator">50 * 1.28</gadget>
<output>64</output>

<result>64</result>