When a tree was first planted, it was 4 feet tall, and the height of the tree increased by a constant amount each year for the next 6 years. At the end of the 6th year , the tree was 1/5 taller than it was at the end of the 4th year. By how many feet did the height of the tree increase each year?
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发表于 2008-10-9 09:04:00
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