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1、,小数乘小数(三),1、口算:,0.230.2=,0.232=,0.2320=,0.4510=,0.451=,0.450.1=,1.20.4=,1.24=,1.240=,0.046,0.46,4.6,40.5,4.05,0.405,48,4.8,0.48,观察这些算式,你有什么发现?,2、不计算,你能直接比较大小吗?,0.651.02 0.65,2.280.98 2.28,探究一,小巧家的这三部分的面积分别是多少呢?,下面是小巧家的阳台平面图,阳台长3.2米,宽1.5米。,探究一,1.5,2.4,0.9,探究一,这些题的答案又是多少?,因数,因数,0.16,14.28,3.36,0.672,8
2、.82,3.78,4.2,1.51=1.5,4.21=4.2,1.51.6=2.4,4.23.4=14.28 4.22.1=8.82,1.50.6=0.9,4.20.8=3.36 4.20.16=0.672 4.20.9=3.78,将上述九个算式分分类,你会怎么分呢?,探究二,结论: 如果两个因数都大于0,那么: 一个数乘大于1的数,积 原来的数; 一个数乘小于1的数,积 原来的数; 一个数乘等于1的数,积 原来的数。,2、不计算,你能直接比较初步大小吗?,0.651.02 0.65,2.280.98 2.28,练习一,在下面的里填上符号“”、“” 或“”。,0.871.2,0.87,0.87
3、1,0.870.2,0.87,0.87,1.60.5,1.6,1.61.5,1.60.1,1.6,0.87,=,练习二,2.5,=,0.4,1.06,2.7,0.08,1,2.65,6.75,0.2,0.39,=,20.1,0.03,1.6,0.52,7.839,0.0117,0.624,0.2028,先说一说积比第一个因数大还是小,再计算。,练习三,不计算,判断下面各题的得数是否正确。,0.560.25=1.4,9.81.06=9.388,3.010.49=14.749,0.243.5=0.24,(),( ),(),(),练习四: 根据“45 98=4410”,在下列算式中点上小数点,使算式成立。,(1) 4.6 9.8 = 45 08 (2) 4.6 0.98 = 4 508 (3)0. 46 0.098 = 4508 (4)0.046 9.8 = 4508,.,.,0.0,0.,本课小结,通过今天的学习你有什么新的收获?谁愿意来和大家一起分享一下。,课后作业,一、口算,二、填空6题(略),3.6 0.4=,7.8 0.7=,4.1 2=,2.9 1.2=,1.05 1=,20.1 0.3=,