An express train and a slow train drive from place A to place B at the same time, when the express train travels 1/2 of the full distance, the slow train is still 54 kilometers away from place B; when the express train reaches the destination, the slow train travels the full distance (4/5), how many kilometers is the distance between A and B?
一辆快车和一辆慢车同时从甲地开往乙地，当快车行了全程的(1/2)时，慢车离乙地还有54千米；当快车到达终点时，慢车行了全程的(4/5)，甲乙两地相距多少千米？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(4/5) * (1/2)</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">54 / (3/5)</gadget>
<output>90</output>

<result>90</result>