推荐一些GRE数学填空题练习题及解析

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摘要：以下是一些 GRE 数学填空题练习题及解析：

以下是一些 GRE 数学填空题练习题及解析：

The average (arithmetic-mean) of the 11 numbers in a list is 14. If the average of 9 of the numbers in the list is 9, what is the average of the other 2 numbers?
- 答案：24
- 解析：11 个数的算术平均数是 14，则这 11 个数的总和为 11×14=154。其中 9 个数的算术平均数为 9，则这 9 个数的总和为 9×9=81。那么剩下的 2 个数的总和为 154-81=73，所以这 2 个数的平均数为 73÷2=36.5。
According to a tax rate formula for a certain year, the amount of tax owed by an individual whose annual income was between $31,850 and $77,100 was equal to a base tax of $4,386 plus 24 percent of the annual income that exceeded $31,850. According to this formula, what was the amount of tax owed by an individual whose annual income that year was $42,000?
- 答案：$6,822
- 解析：首先计算出超过$31,850 的部分，即$42,000 - $31,850 = $10,150。然后，计算这部分的 24%，即$10,150 × 0.24 = $2,436。最后，将 base tax of $4,386 和额外的$2,436 相加，得到$4,386 + $2,436 = $6,822。
A certain band will perform 15 different songs in random order, and no song will be performed twice. If 9 of the songs are new, what is the probability that the first 2 songs that the band performs will both be new?
- 答案：12/35
- 解析：首先，计算从 15 首歌曲中选择 2 首歌曲的总组合数，即。然后，计算从 9 首新歌中选择 2 首歌曲的组合数，即。最后，将新歌的组合数除以总组合数，得到概率为。