第2单元20以内的退位减法第1课时十几减9课件

第1课时十几减920以内的退位减法义务教育人教版一年级下册2 抢答。9+4112323开始139+7169+5149+3129+9189+21110+515结束复习导入10-9116-31318-41412-102 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com探究新知 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com1你从图中知道了哪些信息？要求的问题是什么？谁能完整地说说这个题目的意思？ www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com用减法计算。已知：有15个气球，卖了9个。问题：还有几个？15-9讨论：该怎么计算呢？用自己的方法试着算一算，并和同学交流你的想法。表示总数表示部分求另一部分 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com15-9=方法一：点数法6表示卖出9个 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com15-9=方法二：平十法65415－5=1010－4=6－10－ www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com15-9=方法三：610－9=11＋5=61051-+破十法 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com15-9=方法四：想加算减法69+=1515-9=66你是怎样计算的？ www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com做一做11-9=16-9=1.用摆一摆，算一算。27 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com2.圈一圈，算一算。说说你是怎么想的？17-9=14-9=58 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com13－9＝19－9＝12－9＝18－9＝41039仔细观察这些算式，你发现了什么？十几减9的结果就是“几”加1。3.用你喜欢的方法计算。 1114151718121316－9934268751.巩固练习 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com问题：（1）你从题中知道了什么？（2）要求的问题是什么？（3）你能试着解决这个问题吗？2. www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com白狐狸：16－9＝红狐狸：9－3＝谁剩的苹果多？白狐狸剩的苹果多。7（个）6（个）7＞62. www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com课堂小结十几减9的计算方法：“点数法”、“平十法”、“破十法”、“想加算减法”等，其中“破十法”较为常用。