The fast train and the slow train leave opposite places respectively from A and B. After 4 hours, the express train is still 120 kilometers away from B, and the slow train is still 120 kilometers away from A (2/5). It is known that the fast train travels 15 kilometers longer than the slow train per hour. How many kilometers are there between A and B?
快、慢两车分别从甲、乙两地相对开出，4小时后，快车距乙地还有120千米，慢车距甲地还有全程的(2/5)．已知快车每小时比慢车多行15千米．甲、乙两地相距多少千米？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">120 + 60</gadget>
<output>180</output>

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

<gadget id="calculator">(2/5) - 1</gadget>
<output>-3/5 = around -0.6</output>

<gadget id="calculator">1 + (-3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">180 / (2/5)</gadget>
<output>450</output>

<result>450</result>