The express train and the slow train start from A and B at the same time and run toward each other. It takes 10 hours for the express train to complete AB, and 15 hours for the slow train to complete AB. The fast and slow cars return immediately after arriving at their respective destinations. The place where the two cars meet for the second time is 120 kilometers away from the midpoint of A and B. Find the distance between A and B?
快车与慢车同时从A、B两地出发相向而行，快车行完AB全程要10小时，慢车行完AB全程15小时．快、慢两车到达各自目的地后立即返回，两车第二次相遇的地点距离A、B两地的中点有120千米，求A、B相距？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 * (2/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(6/5) - 1</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">120 / (3/10)</gadget>
<output>400</output>

<result>400</result>