1．Is the integer n odd? (1) n is divisible by 3. (2) 2n is divisible by twice as many positive integers as n.这句我看不懂是什么意思
3．The lifetimes of all the batteries produced by a certain company in a year have a distribution that is symmetric about the mean m. If the distribution has a standard deviation of d, what percent of the distribution is greater than m + d ? 这个问句是什么意思？到底要求标准差的什么呢？ (1) 68 percent of the distribution lies in the interval from m - d to m + d, inclusive. (2) 16 percent of the distribution is less than m - d.
4．The arithmetic mean and standard deviation of a certain normal distribution are 13.5 and 1.5, respectively. What value is exactly 2 standard deviations less than the mean? 也是没懂这个到底要求标准差的什么？ (A) 10.5 (B) 11.0 (C) 11.5 (D) 12.0 (E) 12.5
7．For a certain race, 3 teams were allowed to enter 3 members each. A team earned 6 - n points whenever one of its members finished in nth place, where 1 <= n <= 5. There were no ties, disqualifications, or withdrawals. If no team earned more than 6 points, what is the least possible score a team could have earned? (A) 0 (B) 1 (C) 2 (D) 3 (E) 4
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发表于 2009-7-4 10:16:00
