估算:61÷2≈ 79÷4≈ 38÷6≈ 99×7≈ 298×5≈ 702×3≈
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=