The express train and the slow train are traveling towards each other from places A and B which are 600 kilometers apart at the same time, and meet at a distance of 30 kilometers from the midpoint of the two places. It is known that the express train travels 110 kilometers per hour, how many kilometers per hour does the slow train travel?
快车和慢车同时从相距600千米的A、B两地相向而行，在离两地中点30千米处相遇，已知快车每小时行110千米，则慢车每小时行多少千米？
<gadget id="calculator">600 / 2</gadget>
<output>300</output>

<gadget id="calculator">300 - 30</gadget>
<output>270</output>

<gadget id="calculator">300 + 30</gadget>
<output>330</output>

<gadget id="calculator">330 / 110</gadget>
<output>3</output>

<gadget id="calculator">270 / 3</gadget>
<output>90</output>

<result>90</result>