A car goes from Station A to Station B at a certain speed. It is known that when it leaves Station B for 9 minutes, the car leaves Station A for 10 kilometers. After driving for another quarter of an hour, the car leaves station A for 20 kilometers, and after driving for another half hour, how many kilometers does the car leave station A?
汽车从甲站经过乙站以一定的速度开往丙站，已知离开乙站9分钟时，汽车离开甲站10千米．又行驶一刻钟，汽车离开甲站20千米，再行驶半小时，汽车离开甲站多少千米？
<gadget id="calculator">20 - 10</gadget>
<output>10</output>

<gadget id="calculator">10 / 15</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) * 30</gadget>
<output>20</output>

<gadget id="calculator">20 + 20</gadget>
<output>40</output>

<result>40</result>