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It takes 7 hours to drain off the water tank, while 10 hours to fill it up. For a full water tank, both the water-discharge valve and fill-in valve open for an hour first. Afterwards, the fill-in valve is closed. If so, then how many hours will it still take to drain off the water tank?
Give your answer as a decimal.
Give your answer as a decimal.
6.7 显示答案
以上解析由 考满分老师提供。
