From A to B, it takes 20 hours by express train and 30 hours by slow train. Now the fast and slow cars are traveling towards each other from two places at the same time. After 10 hours, the distance between the two cars is 200km. How many kilometers are the distance between A and B?
从甲地到乙地，快车要20小时，慢车要30小时．现快、慢两车分别从两地同时相向而行，经过10小时两车还相距200km，甲、乙两地相距多少千米？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 10</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 - (5/6)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">200 / (1/6)</gadget>
<output>1_200</output>

<result>1_200</result>