A train originally travels 60 kilometers per hour, and it takes 16.2 hours to travel from city A to city B. After the train speeds up, it can travel 90 kilometers per hour. Now, how many hours earlier can it arrive from city A to city B?
一列火车原来每小时行驶60千米，从甲城到乙城需要16.2小时，火车提速后，每小时可以行驶90千米，现在从甲城到乙城，可以提前几小时到达？
<gadget id="calculator">16.2 / 90</gadget>
<output>0.18</output>

<gadget id="calculator">60 * 0.18</gadget>
<output>10.8</output>

<gadget id="calculator">16.2 - 10.8</gadget>
<output>5.4</output>

<result>5.4</result>