20以内的退位减法整理与复习.ppt

1、第二单元 20以内退位减法,人教版数学一年级下册,整理和复习,介绍两位新朋友,我叫聪聪,我叫明明,以后学习中有什么困难，我们就会来帮助你们！,你准行!,找规律填一填,11-9 12-9 13-9 14-9 15-9 16-9 17-9 18-9,11-8 12-8 13-8 14-8 15-8 16-8 17-8,11-7 12-7 13-7 14-7 15-7 16-7,11-6 12-6 13-6 14-6 15-6,11-5 12-5 13-5 14-5,11-4 12-4 13-4,11-3 12-3,11-2,同桌讨论:用什么方法计算这些减法？,我用想加算减,我用十来减,退位减，我会

2、算：十几减9，几加1，十几减8，几加2， 十几减7，几加3， 十几减6，几加4，十几减5，几加5。,20以内退位减法表,从减法表中你能看出什么规律？,11-9,11-8,11-7,11-6,11-5,11-4,11-3,11-2,12-9,12-8,12-7,12-6,12-5,12-4,12-3,11,11,11,11,11,11,11,11,9,8,7,6,5,4,3,2,13-9,13-8,13-7,13-6,13-5,13-4,14-9,14-8,14-7,14-6,14-5,15-9,15-8,15-7,15-6,16-9,16-8,16-7,17-9,17-8,18-9,12,12

3、,12,12,12,12,12,13,13,13,13,13,13,14,14,14,14,14,15,15,15,15,16,16,16,17,17,18,20以内退位减法表,9,8,7,6,5,4,3,9,8,7,6,5,4,9,8,7,6,5,9,8,7,6,9,8,7,9,8,9,竖着看,减数不变，,11-9,11-8,11-7,11-6,11-5,11-4,11-3,11-2,12-9,12-8,12-7,12-6,12-5,12-4,12-3,13-9,13-8,13-7,13-6,13-5,13-4,14-9,14-8,14-7,14-6,14-5,15-9,15-8,15-7,

4、15-6,16-9,16-8,16-7,17-9,17-8,18-9,20以内退位减法表,横着看,11,12,13,14,15,16,17,18,9,9,9,9,9,9,9,9,11,12,13,14,15,16,17,8,8,8,8,8,8,8,7,7,7,7,7,7,6,6,6,6,6,11,12,13,14,15,16,11,12,13,14,15,11,12,13,14,11,12,13,11,12,11,5,5,5,5,4,4,4,3,3,2,被减数不变，减数依次减少1，差依次增加1。,11-9,11-8,11-7,11-6,11-5,11-4,11-3,11-2,12-9,12-8

5、,12-7,12-6,12-5,12-4,12-3,13-9,13-8,13-7,13-6,13-5,13-4,14-9,14-8,14-7,14-6,14-5,15-9,15-8,15-7,15-6,16-9,16-8,16-7,17-9,17-8,18-9,20以内退位减法表,斜着看,18,17,16,15,14,13,12,11,9,8,7,6,5,4,3,2,17,16,15,14,13,12,11,9,8,7,6,5,4,3,16,15,14,13,12,11,9,8,7,6,5,4,15,14,13,12,11,9,8,7,6,5,被减数、减数依次增加1，差不变。,被减数不变，减数

6、依次减少1，差依次增加1。,减数不变，,被减数、减数依次增加1，差不变。,减数不变，,被减数不变，减数依次减少1，差依次增加1。,被减数、减数依次增加1，差不变。,看图列算式,想加算减,3+8= 4+9= 5+7= 113= 134= 125= 118= 139= 127=,11,8,3,13,9,4,12,7,5,12-9= 13-8=,看谁算得又对又快！,17-9= 15-8= 18-9= 17-8= 16-9=,12-9= 19-9= 14-3= 14-9=,任选方法进行计算：,摘果子,12 - 3 = 9,13 - 8 = 5,13 - 6 = 7,11 - 8 = 3,15 - 7 =