整数乘法运算定律推广到小数乘法ppt课件.ppt

整数运算定律推广到小数,1、口算：,0.51.42=3.20.7=16.80.68=12.50.3=,0.71,2.24,16.12,3.75,5.2+12.9=105.4=25.22=332.9=,18.1,4.6,50.4,98.7,12.50.8=16.896.89=0.961000=40.25=,10,10,960,1,男生组 女生组0.81.3 1.30.8(0.90.4)0.5 0.9(0.40.5)(3.2+2.8)0.6 3.20.6+2.80.6,2、分组计算,整数乘法的运算律，对小数乘法也同样适用。,用简便方法计算0.250.734 0.1543,小数乘法简算应注意的问题：一审：审清题目。二看：观察数字特征，选择比较简便的算法。三算：认真计算。四查：查运算顺序；查数字；查每一步的计算。,做一做：7.60.8+0.27.60.2536 0.8599,笔算，并用应用乘法交换律验算3.54.80.370.25 1.90.18,=0.49,=0.35,=11,=0.08,=0.48,=0.3,巩固练习:,1、根据运算定律填空：a+6.45+7.2=6.45+(y)4.2=(4.2)a3.4+3.4b=(a+b),2、判断：（对的打，错的打）0.20.6=0.30.4应用了乘法的交换律（）4.9+4.94.9=4.9(1+4.9)()5.6+5.6+2.45.6=5.6(5.6+2.4)（）,a,7.2,y,3.4,7、用简便方法计算。,0.258.54=0.2548.5=18.5=8.52.41.02=2.4（10.02）=2.412.40.02=2.40.048=2.448,1.288.60.728.6=（1.280.72）8.6=28.6=17.2 12.50.960.8=12.50.80.96=100.96=9.6,=1.462,=2.345,=0.312,12.54480=12.58044=100044=44000（千克）=44（吨）,3、能用简便方法的就用简便方法计算下面各题，并说说应用了哪些运算定律.,18.76-3.47-0.53 3.2+0.8-3.2+0.8,7.810.1 363.4+366.6 0.22.5,B、拓展练习1.2510.80.8 9.825,2.5(0.4+0.04)3.571.2-3.570.2,9.999 4.6299+4.624.94.9+0.49,