Uncle Li transported a batch of goods from place A to place B, which is 270 kilometers away. Travel 40 kilometers per hour when going, and travel 60 kilometers per hour when returning. Find the average round trip speed of Uncle Li.
李叔叔把一批货从甲地运往相距270千米的乙地．去时每小时行40千米，返回时每小时行60千米．求李叔叔往返的平均速度．
<gadget id="calculator">270 * 2</gadget>
<output>540</output>

<gadget id="calculator">270 / 40</gadget>
<output>27/4 = around 6.75</output>

<gadget id="calculator">270 / 60</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(27/4) + (9/2)</gadget>
<output>45/4 = around 11.25</output>

<gadget id="calculator">540 / (45/4)</gadget>
<output>48</output>

<result>48</result>