The express train and the local train depart from the east and west stations at the same time, and meet for the first time at 10 kilometers west of the midpoint. After meeting, the two cars move forward at the same speed. At this time, the meeting point is 40 kilometers away from the East Railway Station. How many kilometers is the distance between the east and west stations?
快车和慢车同时从东西两站相对开出，第一次在中点西侧10千米处相遇，相遇后两车以原速前进，到达对方出发地后，两车立即返回，在途中第二次相遇，这时相遇点距离东站40千米．东西两站相距多少千米？
<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<gadget id="calculator">30 + 40</gadget>
<output>70</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">2 - (3/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">70 / (1/2)</gadget>
<output>140</output>

<result>140</result>