问题
单项选择题
Two hundred multiples of seven are chosen at random, and 300 multiples of eight are chosen at random. Approximately what percentage of the 500 selected numbers are odd ？（）
A. 20%
B. 25%
C. 40%
D. 5O%
E. 80%
答案
参考答案：A
解析：
All multiples of 8 are even, and half of the multiples of 7 are odd; the multiples of 7 make up 2/5 of the total, so if 1/2 of those multiples of 7 are odd, then 1/5 of the total will be odd, or 20%.