It takes Xiao Li and Xiao Gang 30 minutes and 50 minutes to travel from A to B respectively. If two people start from places A and B at the same time and walk towards each other, and when they meet, Li has traveled 4 kilometers, how many kilometers is the total length?
小李和小刚从甲地到乙地分别要30分钟和50分钟．如果两人分别从甲乙两地同时出发相向而行，相遇时小李行了4千米，求全长是多少千米？
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