A car travels 42 kilometers per hour when going from place A to place B, and travels 56 kilometers per hour when returning, what is the average speed of the round trip in kilometers per hour?
一辆汽车从甲地到乙地，去时每小时行42千米，返回时每小时行56千米，则往返的平均速度为每小时多少千米．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 42</gadget>
<output>1/42 = around 0.02381</output>

<gadget id="calculator">1 / 56</gadget>
<output>1/56 = around 0.017857</output>

<gadget id="calculator">(1/42) + (1/56)</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">2 / (1/24)</gadget>
<output>48</output>

<result>48</result>