truck travels 40 kilometers per hour from place A to B. It has been traveling for 4.5 hours. At this time, the ratio of the traveled distance to the untraveled distance is 3:7. How many kilometers are left? At this speed, how many hours will it take to reach B?
一辆卡车从甲地到乙，每小时行40千米，已经行了4.5小时，这时已行路程和未行路程的比是3：7，剩下的路程还有多少千米？照这样的速度，还要几个小时才到达乙地？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">4.5 / (3/7)</gadget>
<output>10.5</output>

<gadget id="calculator">40 * 10.5</gadget>
<output>420</output>

<gadget id="calculator">420 / 40</gadget>
<output>21/2 = around 10.5</output>

<result>21/2 = around 10.5</result>