This year, there was a flood in Pingyang mountainous area. At that time, it was measured that the water in a river bed doubled every hour from the beginning of the flood, and the river bed was full in 10 hours. For the safety of the people, all personnel must evacuate when the river water reaches (1/8) of the river bed. How many h.
今年平阳山区发洪水，当时测得一河床中的水从洪水暴发开始每小时上涨1倍，10h涨满河床．为了人民群众的生命安全，所有人员在河水涨到河床的(1/8)时，必须撤离．从洪水暴发到所有人员撤离，有多少h．
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