When an ocean liner dropped anchor, Mrs. Smith did not leave her cabin because she felt unwell. At noon, the porthole beside her bed was 7 meters above the water. At high tide, the water surface rises at a rate of 1 meter per hour. Imagine, if the rate of rising water doubles every hour, how long will it take for the water to level with her porthole? Why?
一艘远洋客轮抛锚泊船时，史密斯夫人因感到不适而没有离开客舱．中午，她床边的舷窗距水面7米．涨潮时，水面以1米每小时的速度上升．设想一下，如果水面上升的速度每小时增加1倍，水面与她的舷窗持平需要多长时间？为什么？
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