口算。⑴4+5= 5+7= 10+90=⑵35+2= 4+9= 20+80=⑶7+3 = 5+6= 30+70=⑷4+60= 7+7= 100-20=
11+5+1= 12+7-1=
12-3-5= 19-2-4= 15-7-4=18-6-8= 17-6-9= 19-9-8
16-1+2= 17-2+4= 8+9-7= 17-9+2=12+3-7= 14+6-2= 10+4-8= 10-7+1=
9-3+1= 16-7+4= 13-3+9=19-3+1= 14-1+5= 8-4+12=
想一想,填一填。15+4-6= 9-5+11= 10-4-3= 3+13-4=