Each set of data, the average output, precise arrives decimally hind, every single line should mean.
每组数据, 输出其平均数, 精确到小数点后3位, 每个平均数应该单独占一行.
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Average output fell by more than a third to the mid - 1990 s, then stagnated until 1999.
上世纪90年代 中期,这一地区平均产量下降超过30%, 此后直至1999年始终未见起色.
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