+= ﹣= += +=1+= 2﹣1= ﹣= 3﹣=1+2= ×= 7﹣4= ×13=×4= 8×= ÷= 5÷=÷8= 8÷= 3÷= ÷=
720里面有几个90？
练习打字． 笑笑2分打字74个，淘气3分打字96个，谁打字的速度比较快？
估计，再计算． 483÷64 236÷35 382÷57．
先说一说把除数看作几十来试商，然后计算．
下面的算法对吗？把不对的改正过来．
+
= 
﹣
= 
+
= 
+
=
+
= 2
﹣1
= 
﹣
= 3
﹣
=
+2
= 
= 7﹣4
= 
×13
=
×4= 8×
= 
÷
= 5÷
=
÷8= 8÷
= 3
÷
= 
÷
=
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