The total length of the Shanghai-Nanjing Expressway is 270 kilometers. The truck departed from Nanjing and headed for Shanghai along the Shanghai-Nanjing Expressway, traveling 90 kilometers per hour. It has been traveling for 2 hours. How many hours does it take for the truck to go to Shanghai?
沪宁高速公路全长270千米．卡车从南京出发，沿沪宁高速公路开往上海，每小时行90千米，已经行了2小时．卡车到上海还要行几小时？
<gadget id="calculator">90 * 2</gadget>
<output>180</output>

<gadget id="calculator">270 - 180</gadget>
<output>90</output>

<gadget id="calculator">90 / 90</gadget>
<output>1</output>

<result>1</result>