估算: 127×8≈ 3×78≈ 92×6≈ 88×4≈ 6×39≈ 99×7≈ 58×2≈ 63×5≈
1+10= 10+2= 10+6= 10+9= 10+7= 0+10=
10+3= 10+6= 9+10= 5+10= 7+10= 10+8=
10+2= 10+3=10+5= 3+10= 4+10= 6+10=
7-0= 6-1= 7-3= 8-5= 4-2= 9-7=
5+0= 10-2= 5-2= 7-3= 6-4= 8-4=