car travels from A to B at an average of 20 kilometers per hour. After arriving at point B, return to point A at a speed of 30 kilometers per hour, and the round trip takes 7.5 hours. Find the distance between A and B.
一辆汽车从甲地开往乙地，平均每小时行20千米．到乙地后又以每小时30千米的速度返回甲地，往返一次共用7.5小时．求甲乙两地间的路程．
<gadget id="calculator">7.5 * 30</gadget>
<output>225</output>

<gadget id="calculator">20 + 30</gadget>
<output>50</output>

<gadget id="calculator">225 / 50</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">20 * (9/2)</gadget>
<output>90</output>

<result>90</result>