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VALUE OF IMPORTS TO AND EXPORTS FROM COUNTRY T, 2000-2009[img]2014m9x/ct_egreqj

游客2024-01-12  20
问题 VALUE OF IMPORTS TO AND EXPORTS FROM COUNTRY T, 2000-2009
[br] Hard Question
If it were discovered that the value of imports shown for 2007 was incorrect and should have been $5 billion instead, then the average(arithmetic mean)value of imports per year for the 10 years shown would have been approximately how much less?
选项 A、$200 million
B、$50 million
C、$20 million
D、$7 million
E、$5 million
答案 A
解析 To answer this question, you do not need to compute either of the two 10-year averages referred to in the question; you just need to calculate the difference between the two averages.
    The average value of imports for the 10 years shown in the graph is found by adding the 10 values and then dividing the sum by 10. The value of imports in 2007 is $7 billion. If that amount were $5 billion instead, then the sum of the values would be $2 billion less. If the sum were $2 billion less than what it was, then the average would decrease by 2 billion divided by 10, or = 200,000,000. The average would therefore be $200 million less, and the correct answer is Choice A.
    A more algebraic approach to the problem is to let S represent the sum, in billions, of the 10 values of imports in the graph. The average of the 10 values is S/10. Note that S - 2 represents the sum, in billions, of the 10 values adjusted for the $2 billion correction for 2007. The average of the adjusted sum is. The difference between the two averages is

The difference is 0.2 billion dollars, or $200 million. The correct answer is Choice A.
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