The distance between A and B is 800 kilometers. A car travels from A to B at 40 kilometers per hour and speeds up by 20 kilometers when returning. What is the average speed of this car going back and forth between the two places in kilometers per hour?
甲乙两地相距800千米，一辆汽车从甲地开往乙地，每小时行40千米，返回时速度加快20千米，这辆汽车往返两地的平均速度是每小时多少千米．
<gadget id="calculator">800 / 40</gadget>
<output>20</output>

<gadget id="calculator">40 + 20</gadget>
<output>60</output>

<gadget id="calculator">800 / 60</gadget>
<output>40/3 = around 13.333333</output>

<gadget id="calculator">20 + (40/3)</gadget>
<output>100/3 = around 33.333333</output>

<gadget id="calculator">2 / (100/3)</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">800 * (3/50)</gadget>
<output>48</output>

<result>48</result>