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
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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
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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
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