计算．21÷18÷15÷反思计算上面的题目以后，你发现了什么？能结合具体的例子说说为什么吗？试着计算下面的题目．不计算，你能比较算式的大小吗？15÷ ×159÷ 9×．
8÷÷12÷．
口算题．= 3= ÷6=6= = == =
= = == = =
计算．
÷12
÷
．
= 3
= 
÷6=
= 
= 
=
= 
=
= 
= 
=
= 
= 
=
．
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