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题库 / OG2017Q-PS-55
After 4,000 gallons of water were added to a large water tank that was already filled to ~$\frac{3}{4}$~of its capacity, the tank was then at ~$\frac{4}{5}$~ of its capacity. How many gallons of water does the tank hold when filled to capacity?
5,000
6,200
20,000
40,000
80,000
题目分析：
这种问题简单直接不易出错的方法就是列一元一次方程.假设容器的容量为 L.根据题意:~$\frac{4}{5}L=4000+\frac{3}{4}L$~,解方程得出 L=80,000.
综上：答案就是E