The distance between A and B is 10 kilometers. Both the fast and slow trains are driving from A to B. When the fast train leaves, the slow train has already driven 1.5 kilometers away. When the express train arrives at point B, the slow train is still 1 kilometer away from point B. Then, how many kilometers away from point B is the express train catching up with the slow train?
甲、乙两地相距10千米，快、慢两车都从甲开往乙，快车出发时，慢车已开出1.5千米．当快车到达乙地时，慢车距乙地还有1千米，那么，快车是距乙地几千米处追上慢车的？
<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<gadget id="calculator">1.5 / 1</gadget>
<output>1.5</output>

<gadget id="calculator">1.5 * 4</gadget>
<output>6</output>

<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<result>4</result>