课件19张PPT。整数加法运算定律推广到小数大家好!我是数学小博士46+32+54+168=300480-37-263=180 + + +
=(46+54)+(32+168)
=100+200
=300 480-37-263
=480-(37+263)
=480-300
=180463254168==新知探究下面每组算式两边的结果是相等吗?请你算一算a+b=b+a(a+b)+c=a+(b+c)加法交换律加法结合律0.6元7.91元3.4元0.09元这些文具一共花了多少钱?0.6+7.91+3.4+0.09(1)6.7+4.95+3.3 = 6.7+ +4.953.3巩固练习第一关0.38+0.36+2.64
3.9+4.08+3.92+1.1
5.17-1.8-3.2
4.02-3.5+0.98
计算下面各题,怎样简便就怎样计算第二关=0.38+(0.36+2.64)=0.38+3=3.380.38+0.36+2.64=(3.9+1.1)+(4.08+3.92)=5+8=133.9+4.08+3.92+1.12. 计算下面各题,怎样简便就怎样计算。巩固练习5.17-1.8-3.2=5.17-(1.8+3.2)=5.17-5=0.174.02-3.5+0.98=4.02+0.98-3.5=5-3.5=1.53. 计算下面各题,怎样简便就怎样计算。巩固练习第三关动脑巧算:
(7.86+7.86+7.86+7.86)X25动脑巧算:
(7.86+7.86+7.86+7.86)X25=7.86x4x25=7.86x(4x25)=7.86x100=786 6.55+5.80+2.20=14.55(元)=6.55+(5.80+2.20)答:一共14.55 元。=6.55+84. 开心超市。27.606.5513.405.802.2022.25蛋糕火腿肠口香糖饼干牛奶酸奶巩固练习