A, B, and C travel between A and B. A starts from A, and C starts from B at the same time. After 30 minutes, B also starts from B. B meets A after 3 hours, and A and C meet after another hour. It is known that A's speed is 18 kilometers per hour, and B's speed is twice that of C's speed, what is the distance in kilometers between A and B?
甲、乙、丙三人往返于A、B两地．甲从A地出发，丙同时从B地出发，30分钟后乙也从B出发，乙出发3小时后与甲相遇，又过了1个小时，甲和丙才相遇．已知甲的速度是每小时18千米，乙的速度是丙速度的2倍，则AB两地间的距离是多少千米．
<gadget id="calculator">3 * 18</gadget>
<output>54</output>

<gadget id="calculator">0.5 * 18</gadget>
<output>9</output>

<gadget id="calculator">18 * 3</gadget>
<output>54</output>

<gadget id="calculator">18 * 0.5</gadget>
<output>9</output>

<gadget id="calculator">18 - 54 - 9</gadget>
<output>-45</output>

<gadget id="calculator">54 + 9 + (-45)</gadget>
<output>18</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 * (1/2)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">0.5 * (1/2)</gadget>
<output>0.25</output>

<gadget id="calculator">3 - (3/2) - 0.25 - (1/2)</gadget>
<output>0.75</output>

<gadget id="calculator">18 / 0.75</gadget>
<output>24</output>

<gadget id="calculator">24 * 3</gadget>
<output>72</output>

<gadget id="calculator">3 + 0.5</gadget>
<output>3.5</output>

<gadget id="calculator">18 * 3.5</gadget>
<output>63</output>

<gadget id="calculator">72 + 63</gadget>
<output>135</output>

<result>135</result>