Two cars, A and B, start from A and B at the same time. A completes the journey in 4 hours, and B completes the journey in 5 hours. When A arrives at B, B is still 100 kilometers away from A. km?
甲、乙两车同时从A、B两地相对开出，甲4小时行完全程，乙5小时行完全程，甲到达B地时，乙离A地还有100千米，则全程有多少千米？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 4</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 / (1/5)</gadget>
<output>500</output>

<result>500</result>