Xiaoming's uphill speed is 3.6 kilometers per hour, and his downhill speed is 4.5 kilometers per hour. There is a slope. Xiaoming first goes uphill and then returns to the original road. It takes 1.8 hours. What is the total length of this slope in kilometers?
小明上坡速度为每小时3.6千米，下坡时每小时4.5千米，有一个斜坡，小明先上坡再原路返回共用1.8小时，这段斜坡全长多少千米．
<gadget id="calculator">1 / 3.6</gadget>
<output>0.277778</output>

<gadget id="calculator">1 / 4.5</gadget>
<output>0.222222</output>

<gadget id="calculator">0.277778 + 0.222222</gadget>
<output>0.5</output>

<gadget id="calculator">1.8 / 0.5</gadget>
<output>3.6</output>

<result>3.6</result>