From A to B, travel 60 kilometers per hour, return the same way, 40 kilometers per hour. Find the average speed to and from A and B.
从甲到乙，每小时行60千米，原路返回，每小时40千米．求往返甲乙的平均速度．
<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/60) + (1/40)</gadget>
<output>1/24 = around 0.041667</output>

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

<result>48</result>