Xiao Wang travels between AB and AB by motorcycle, with an average speed of 48 kilometers per hour. If he went at a speed of 42 kilometers per hour, how many kilometers per hour did he travel on average when he returned?
小王骑摩托车往返AB两地，平均速度为每小时48千米．如果他去时速度是每小时行42千米，那么他返回平均每小时行多少千米？
<gadget id="calculator">2 / 48</gadget>
<output>1/24 = around 0.041667</output>

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

<gadget id="calculator">(1/24) - (1/42)</gadget>
<output>1/56 = around 0.017857</output>

<gadget id="calculator">1 / (1/56)</gadget>
<output>56</output>

<result>56</result>