Two cars, A and B, drive from places a and b respectively. When they meet, car A travels 70% of the journey, and car B is still 320 kilometers away from the midpoint. How many kilometers are there between places a and b?
甲乙两车分别从a，b两地相对开出，相遇时甲车行了全程的70%，乙车距离中点还有320千米，则a，b两地相距多少千米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">320 / (1/5)</gadget>
<output>1_600</output>

<result>1_600</result>