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www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com如果有括号,要先算括号里面的。和整数加、减混合运算的顺序相同。按照从左往右的顺序计算。小数加、减法混合运算,该怎样计算呢?探索新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com0.38+0.26+2.65.7-0.81-1.2998.2+32.5-13.4=0.64+2.6=3.24=4.89-1.29=3.6=130.7-13.4=117.31.请脱式计算下面各题。巩固练习三教材做一做 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com2.你会用计算器计算小数加、减混合运算吗?你是怎样输入的,请把它记录下来,并计算出结果。巩固练习三教材做一做 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com从左往右算,先算50-38.5,再算减4.8。你知道计算器是按什么运算顺序计算的吗?50-38.5-4.8=6.750-(38.5+4.8)=6.7我先算括号里的38.5+4.8,把答案记下来,再用50减去它。巩固练习三2. www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com(1)文具盒比钢笔贵多少元?11.40-6.80=4.60(元)答:文具盒比钢笔贵4.60元。巩固练习三3. www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com11.40+6.80+1.20+0.60=18.2+1.2+0.6=19.4+0.6=20(元)答:文具盒、钢笔、三角尺和橡皮一共20元。(2)文具盒、钢笔、三角尺和橡皮一共多少元?巩固练习三3. www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com36.90+11.40=48.30(元)48.30元<50元答:买一个计算器和一个文具盒,50元够。(3)买一个计算器和一个文具盒,50元够吗?巩固练习三3. www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com计算小数加减混合运算应注意:小数加减混合运算的顺序与整数加减混合运算的顺序一样。没有括号的,按照从左到右的顺序计算;有括号的,要先算括号里面的,再算括号外面的。课堂小结四 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com=9.1=8.1=0.82=0.5=3.6=2.3课后练习五教材P77T1 查看更多

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