从甲地到乙地的公路只有上坡路和下坡路,没有平路。一辆汽车上坡时每小时行驶20千米,下坡时每小时行驶35千米,车从甲地开往乙地需9小时,从乙地到甲地需7个半小时。问:甲、乙两地间的公路有多少千米?小白的外婆住在西瓜市,那里和樱桃市之间隔着一座大山。小白小的时候每次去外婆家都要徒步翻山越岭,往往在路上就要花费好几天的时间。不过最近两年,山上铺起了一条公路,小 From A to B, only uphill and downhill roads, there is no road. A car traveling uphill every hour 20 kilometers, downhill driving 35 kilometers per hour, the car from A to B to 9 hours, from B to A to 7 and a half hours. Q: A, B between the two roads how many kilometers? White grandmother live in watermelon city, where there is a big mountain between Cherry City. Small white every time my grandmother have to go hiking across the mountains, often on the road it will take several days. However, the last two years, a mountain paved a road, small