求教两题数学~

zhangfan89

（1）9.4  9.9  9.9  9.9  10.0  10.2  10.2  10.5
The mean and the standard deviation of the 8 numbers shown are 10.0 and 0.3, respectively. What percent of 8 numbers are within 1 standard deviation of the mean?   (ANS:75%)

(2) Is the integer n odd? (ANS:条件2单独可以求出)
    (1) n is divisible by 3
    (2) 2n is divisible by twice as many as positive integers as n

求热心的筒子们解答~

larry686

（1）within 1 standard deviation of the mean 应该是说  10-0.3《 number《 10+0.3 吧
（2）奇数n原来的因数有m个分别是1,3，……n个，这都乘以2 得到 m个因数2,6，……2n，这样2n就有2m个因数了。但是如果是偶数，如4 本来有因数m个分别是1,2,4。  8有1,2,4 然后同样方法都乘以2，得到2,4,8。这样2，4重复两次就不行了，别的偶数一样证明。所以选（b）

ann725

楼上好样的！！！！这要是我在考场上第二题必须答不出～～
顶起来让不会的都来看看～～共同学习学习

guanglin405187

2n is divisible by twice as many as positive integers as n

啥意思？

guanglin405187

哦~