A car travels from A to B at 40 kilometers per hour and 60 kilometers per hour when it returns. A total of 4 hours round trip. What is the distance in kilometers between A and B?
一辆汽车从A地到B地，去时每小时行40千米，回来时每小时行60千米．往返一次共4小时．AB两地间距离是多少千米．
<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

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

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

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

<gadget id="calculator">48 * 4</gadget>
<output>192</output>

<result>192</result>