A, B, and C start at the same time from point A to point B, which is 100 kilometers away from point A. A and C travel by car at a speed of 25 km/h, while B walks at a speed of 5 km/h. After a while, C gets off the car and walks at a speed of 5 km/h, while A turns back at the original speed, picks up B and goes to point B, so that A, B, and C arrive at point B at the same time , how many hours is this trip?
甲、乙、丙三人同时从A地出发去距A地100千米的B地，甲与丙以25千米/时的速度乘车行进，而乙却以5千米/时的速度步行，过了一段时间后，丙下车改以5千米/时的速度步行，而甲驾车以原速折回，将乙载上而前往B地，这样甲、乙、丙三人同时到达B地，此旅程共用时数为多少小时？
<gadget id="calculator">100 * 2</gadget>
<output>200</output>

<gadget id="calculator">200 / 25</gadget>
<output>8</output>

<result>8</result>