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题目材料：
The normal annual precipitation shown for each city is calculated by taking the average (arithmetic mean) of the annual precipitation amounts for that city for the 30-year period 1961-1990. How many inches of precipitation would Dallas have had to receive in 1991 to raise its average annual precipitation for the 31-year period 1961-1991 to $$34.1$$ inches?
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A.33.9
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B.34.5
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C.40.0
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D.46.1
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E.64.7
D显示答案
