估算319×6≈ 53÷6≈ 397+501≈ 287×9≈
8-4= 9-5= 5-5= 3-3= 7-7= 8-7=
9-4= 8-2= 9-7=4-4= 10-5= 4-2=
8-5= 10-3= 9-3=10-7= 7-5= 6-4=
7-4= 6-0= 5-2=10-9= 10-8= 8-2=
5-3= 7-2= 9-1=7-1= 8-5= 6-3=