【案例】448-234 503-302 428-234 503-392 420-234 503-409师:请算好的同学对照竖式,比一比每组的三道题目,看看你有什么发现?(学生思考了半分钟,个别学生就举起了手。我让他们把手放下,继续思考。)(两分钟后开始交流。)生:我从竖式上发现第一道题是不退位减,第二道题点了一个退位点,第三题点了两个退位点。生:我补充,点了两个退位点的叫做连续退位减。生:第二组的第三道题是隔位退位减。 [Case] ​​448-234 503-302 428-234 503-392 420-234 503-409 Teacher: Please count a good classmate vertical control, compared to three groups of three questions, to see what you found? ( Students think half a minute, individual students raised their hands and I let them put their hands down and continue to think.) (Two minutes after the exchange.) Health: I found the first question from the vertical is not abdicated, The second question points a retreat point, the third question points two retreat points. Health: I added, ordered two abort points called continuous abort minus. Students: The third group of questions in the second group is the absentee reduction.