在学习列举法求概率的课堂上,赵老师在黑板上出了这样一道题:某学校举行物理实验操作测试,共准备了三项不同的实验,要求每位学生只参加其中的一项实验,由学生自己抽签确定做哪项实验.在这次测试中,小亮和大刚恰好做同一项实验的概率是.赵老师还告诉同学们,这是2011年山东省聊城市的一道中考题. In the classroom where enumerating the methods for seeking probabilities, Teacher Zhao had a question on the blackboard: a school held physics experiment tests and prepared three different experiments, requiring each student to participate in only one of the experiments. The students draw lots to determine which experiments to perform. In this test, the probability of Xiaoliang and Dagang doing exactly the same experiment is. Teacher Zhao also told the students that this was a test question in Liaocheng, Shandong Province in 2011.