Two cars, fast and slow, leave opposite places at the same time from places A and B, and drive toward each other. When the express train reaches the midpoint of the two places, the slow train has only traveled the full distance (3/8). The two cars continue to move forward and meet at a distance of 40 kilometers from the midpoint. How many kilometers did the express train travel when they met?
快慢两车同时从甲乙两地相对开出，相向而行．当快车到达两地中点时，慢车只行了全程的(3/8)，两车继续前行，在距离中点40千米相遇，相遇时快车行了多少千米？
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(4/7) - (3/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">2 / (1/7)</gadget>
<output>14</output>

<gadget id="calculator">40 * 14</gadget>
<output>560</output>

<gadget id="calculator">560 * (4/7)</gadget>
<output>320</output>

<result>320</result>