一辆客车和一辆货车同时从甲地发往乙地，

当客车到达乙地时，立刻提速50%原路返回甲地，

并在返回的途中遇到了货车，相遇时从两车出发开始算起，恰好经过2小时。

当火车到达乙地时，客车恰好行驶至甲乙两地的中点。

那么当客车返回甲地时，从一开始算起，经过了多少分钟？

数学题解答：原来的速度比是4:3，返回时速度比是6:3=2:1。

货车到达乙地是2又2/5小时。

客车到甲地还需要走5份，每份只要1/5小时、所以还需1小时。

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