根据算式中的数的变化,填写运算符号:
(10________30________20 )________20________60________15
=(300________20)________20________4
=280________20________4
=14________4
=10
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× - ÷ - ÷ - ÷ - ÷ - -
解析分析:根据下一步的结果分析上一步的计算符号.
解答:(10×30-20 )÷20-60÷15
=(300-20)÷20-4
=280÷20-4
=14-4
=10
点评:注意有理数的混合运算顺序:先算乘除,再算加减,遇有括号,先算括号内的.