1、in the question there is no condition to illustrate how many people are in there。so we suppose that there be 10 teachers。
2、condition 1）the number of female teachers is 6：
6/10 *5/9 =1/3 less than 1/2。however， if there are 9 female teachers：
9/10 *8/9 =4/5 more than 1/2。
therefore， this condition is insufficient。
3、condition 2） x/ 10 *（x-1）/9 《 1/10 =》x（x-1）《9
=》x=1，2 or 3
such means that the number of female teachers would be 9，8，or 7
7/10 *6/9 =7/15 less than 1/2
9/10 * 8/9 more than 1/2
therefore， this condition is insufficient too。
referring the condiotion 2， although the number of female teachers is 7，which is more than 5，we cannot confirm whether 俩个都是女老师的概率>1/2吗？
I choose E。
I think because 2 两个都是男老师的概率<1/10 so the probability for 1 male teacher is <(1/10)^1/2 it is about 1/3.3, so for female is >2.3/3.3, for two is just over 1/2.
is it right?
