149. in a share class, both 1st grade student 1/2, 4/5 of 1st grade students have no major, and 2nd grade students who has major is 3 times than that of 1st, ask 2nd have no major A) 1/5 B) 3/10 C) 2/5 D) ??? E) ??? ANS: B
这题答案应该是2/5 设2nd have no major的人数为X 则1/2*(1-x)=3*1/2*1/5
以下是引用miejue在2003-11-17 16:40:00的发言: 149. in a share class, both 1st grade student 1/2, 4/5 of 1st grade students have no major, and 2nd grade students who has major is 3 times than that of 1st, ask 2nd have no major A) 1/5 B) 3/10 C) 2/5 D) ??? E) ??? ANS: B
这题答案应该是2/5 设2nd have no major的人数为X 则1/2*(1-x)=3*1/2*1/5