直接写得数．20×4= 2000×4= 400×5= 600×9=110×8= 240×3= 310×4= 500×2=
=========
++﹣+﹣+﹣．
1﹣．
直接写得数．+ 2+ 1﹣++ 3﹣+﹣﹣﹣．
==+=1﹣= ﹣ +=1+ = 1﹣ =．
=
=
=
=
=
=
=
=
=
+
+
﹣
+
﹣
+
﹣
．
．
+
2+
1﹣
+
+
+
﹣
﹣
﹣
=
=
+
=1﹣
=
+
=1
+ =
1﹣ =
．
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