小学数学人教版四年级下册教学1单元四则运算4课时括号

www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com（2）在96÷（12+4）×2的基础上加上中括号“[]”，变成另一个算式96÷[（12＋4）×2]，运算顺序怎样？第一步：加法：12+4第二步：乘法：（12+4）×2第三步：除法：96÷[（12+4）×2]探索新知二96÷[（12＋4）×2]＝96÷[16×2]＝96÷32＝34.有中括号的运算顺序 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com一个算式里，既有小括号，又有中括号，要先算小括号里面的，再算中括号里面的。探索新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com探索新知二5.总结对比小组交流，说说刚才的这三道算式它们的运算顺序是怎样的？96÷12＋4×296÷（12+4）×296÷[（12＋4）×2]（1）没有括号的要先算乘除，再算加减。（2）有小括号的要先算小括号里面的。（3）既有小括号，又有中括号的，要先算小括号里面的，再算中括号里面的。 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com1.先说一说下面各题的运算顺序，再计算。360÷（70－4×16）＝360÷（70－64）＝360÷6＝60158×[（27＋54）÷9]＝158×[81÷9]＝158×9＝1422巩固练习三教材做一做优翼 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com2.列式计算：（1）43与76的和乘以17与14的差，积是多少？(43+76)×(17-14)=119×3=357巩固练习三 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com（2）125除以84减79的差，商是多少？125÷(84-79)=125÷5=25巩固练习三 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com巩固练习三