Two cars drive from A and B at the same time, and meet each other after 4 hours. At this time, car A has traveled 210 kilometers. It is known that it takes 9 hours for car B to travel from B to A. How many kilometers are there between A and B?
两车同时从A、B两地相对开出，经过4小时相遇，这时甲车行了210千米，已知乙车从B地到A地需要9小时，AB两地相距多少千米？
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

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

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

<gadget id="calculator">210 / (5/9)</gadget>
<output>378</output>

<result>378</result>