GRE官方指南GRE数学真题答案及解析
29.The figure shows a normal distribution with mean m and standard deviation d, including approximate percents of the distribution corresponding to the six regions shown. Suppose the heights of a population of 3,000 adult penguins are approximately normally distributed with a mean of 65 centimeters and a standard deviation of 5 centimeters.
(a) Approximately how many of the adult penguins are between 65 centimeters and 75 centimeters tall?
(b) If an adult penguin is chosen at random from the population, approximately what is the probability that the penguin’s height will be less than 60 centimeters? Give your answer to the nearest 0.05
a.65和75之间，刚好是2个的标准差，因此对应的就是34%+14%=48%了，对应的企鹅是3000*48%=1440了。
B.算的结果应该是2%+14%=16%，最经的0.05应嘎是0.15了
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