Two cars, A and B, are traveling between A and B. It takes 4 hours for A to complete the journey, and 5 hours for B to complete the journey. Two cars drive oppositely from two places at the same time. When they meet, car B is 20 kilometers away from the midpoint of AB. How many miles is the distance between A and B?
甲，乙两辆小轿车在A，B两地之间行驶，甲车行完全程需要4小时，乙车行完全程需要5小时．两辆小轿车同时从两地相对开出，相遇时，乙车距AB中点20千米．A，B两地之间相距多少千米？
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) + (1/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 / (9/20)</gadget>
<output>20/9 = around 2.222222</output>

<gadget id="calculator">(1/4) * (20/9)</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">(1/5) * (20/9)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">(5/9) - (4/9)</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">40 / (1/9)</gadget>
<output>360</output>

<result>360</result>