In flood relief, the PLA sent vehicles to deliver relief supplies. When going there, it travels 42 kilometers per hour, and when it returns, it travels 48 kilometers per hour. If the loading and unloading time is not counted, what is the average speed of the car back and forth in kilometers per hour?
在抗洪救灾中，解放军派车送救灾物资．去时，每小时行42千米，返回时空车，每小时行48千米．如果不计算装缷的时间，车来回的平均速度是每小时多少千米．
<gadget id="calculator">1 / 42</gadget>
<output>1/42 = around 0.02381</output>

<gadget id="calculator">1 / 48</gadget>
<output>1/48 = around 0.020833</output>

<gadget id="calculator">(1/42) + (1/48)</gadget>
<output>5/112 = around 0.044643</output>

<gadget id="calculator">2 / (5/112)</gadget>
<output>224/5 = around 44.8</output>

<result>224/5 = around 44.8</result>