从甲到乙有一段上坡路和下坡路甲骑自行车到乙家上坡每小时行3km,下坡5km,从甲到乙要66分从乙回来要78分

显示全部楼层 · 2012-5-1 11:29:25

设上坡路程为x，下坡路程为y 。v1 = 3km/h ，v2 = 5km/h 。66分钟= 1.1小时，78分钟 =1.3小时。x/3 + y/5 = 1.1x/5 + y/3 = 1.3两式两边同乘以15 得5x + 3y = 16.53x + 5y = 19.525x + 15y = 82.59x + 15y = 58.516x = 24上坡路 x = 1.5 km下坡路 y = 3 km甲乙相距 x+y = 4.5 km...