
甲、乙两车同时从东站开往西站,甲车每小时比乙车多行12千米,甲车行驶4.5小时后到达西站,立即原路返回,
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设甲车速度每小时x千米,乙车速度每小时x-12千米
4.5+31.5/x = (4.5x-31.5)/(x-12)
31.5/x = (4.5x-31.5)/(x-12)-4.5
31.5/x = (4.5x-31.5-4.5x+54)/(x-12)
31.5/x = 22.5 /(x-12)
31.5x-378=22.5x
9x=378
x = 42
即甲车每小时行42千米
4.5+31.5/x = (4.5x-31.5)/(x-12)
31.5/x = (4.5x-31.5)/(x-12)-4.5
31.5/x = (4.5x-31.5-4.5x+54)/(x-12)
31.5/x = 22.5 /(x-12)
31.5x-378=22.5x
9x=378
x = 42
即甲车每小时行42千米
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