一、错题案例笔者到某重点中学七年级学习交流、授课,某次讲授人教版七年级上册第四章第4.3节《角》的习题课,内容涉及与时钟有关夹角、追及问题.当时笔者讲完例题之后,当堂给出一道题目让学生练习.题目如下:小张三点多钟外出买东西时,看手表上的时针和分针的夹角是110°,下午将近四点回家时,发现时针和分针的夹角还是110°,试算出小张外出用了多少时间? First, the wrong question case The author went to a key middle school seventh grade learning exchanges, teaching, a teaching class teaching grade seven chapter fourth chapter 4.3 section “corner” exercises, the content related to the angle of the clock, to catch up with the problem. At that time, after the author finished the example, he gave a subject for students to practice. The topic was as follows: When Zhang Xiaochao went out to buy something more than three minutes, the angle between the hour and minute hands on the watch was 110°, and it was nearly four o’clock in the afternoon. At home, I found that the angle between the hour and minute hands is still 110°. How much time does it take for Zhang to go out?