课件14张PPT。8加几3217255238269278 + ( )= 102108+2+2=128+2+5=158+2+8=188+2+6=168+2+3=138+2=算一算这三个数的和是多少?872108+5=2310138+4=2210128+6=2410148+3=2110118+7=2510158 + 9 = □方法一:方法二:想:9 + 8 = 17 所以:8 + 9 = 178 + 9 = □27 1017圈一圈,算一算8+5=13想一想8 + 5 = □2103 138 + 6 = □24 10148 + 8 = □2106 168+2+2= 8+2+5= 8+4= 8+7= 8+2= 8+3= 8+4= 8+5= 8+6= 8+7= 8+8= 8+9= 8+10= 12121515101316111417121518