人教一下数学第2单元第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+4 139+7 169+5 149+3 129+9 189+2 1110+5 1510-9 116-3 1318-4 1412-10 2还剩几个气球？www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com1原来有15个气球，送出9个。www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com已知：有15个气球，送出9个。问题：还剩几个？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表示送出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666www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com11－9＝ 16－9＝27www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com2. 圈一圈，算一算。17－9＝14－9＝58www.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＝41039十几减9的结果就是“几”加1。 3.934268751.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？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 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。