Two cars set off from AB at the same time and meet at a distance of 40 kilometers from the midpoint. The whole journey takes 10 hours for line A and 15 hours for line B. Find the distance between AB and AB. (answer in multiple ways)
两辆汽车分别从AB两地同时出发，在距中点40千米处相遇，甲行全程需10小时，乙行全程需15小时．求AB两地距离．(用多种方法解答)
<gadget id="calculator">40 + 40</gadget>
<output>80</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6) / 10</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / (1/6) / 15</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">80 / (1/5)</gadget>
<output>400</output>

<result>400</result>