Two trains A and B depart from A and B respectively at the same time, and meet at a distance of 60 km from the midpoint after 4 hours. The express train travels more kilometers per hour than the slow train.
甲、乙两车分别从A、B两站同时相对开出，4小时后在离中点60千米处相遇，快车每小时比慢车多行多少千米．
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">60 * (1/2)</gadget>
<output>30</output>

<result>30</result>