分数乘法的简便计算02.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,第,2,单元,第,1,单元,钟家村小学（本部）,六年级数学,（教研组编）,分数乘法的简便计算二,直接写出得数,1,2,=,1,3,3,4,=,1,2,1,4,=,2,3,2,5,4=,5,8,=,2,5,1,6,1.8,=,7,9,=,3,7,8,7,1=,7,8,5,6,1,6,1,4,8,5,1,4,0.3,1,3,1,直接写出得数,1,3,9 =,2,3,3,4,=,5,6,5,6,2.4=,1,2,1,=,2,3,1,4,=,1,8,5,8,=,1,4,5,6,3,=,5,6,=,3,10,3,8,5,8,3,8,1,2,5,2,1,4,2,填空,1,2,25 =,1,50,1,2,（,）,7,9,（,+,）,27=+,5,27,应用了（）律,应用了（）律,用简便方法计算,1,8,（,+,）,24,1,12,9,11,6,7,35,6,7,18,-,7,18,4,5,3,7,10,-,3,7,3,5,7,5,7,2,3,1,3,+,39,23,38,下面的计算对吗？请说明理由。,3,7,+,4,7,3,2,3,7,（,+,）,4,7,=,3,2,5,7,5,7,+,13,（,13+1,）,=,5,7,1,5,4,5,5,6,5,6,+,（）,1,5,4,5,5,6,=,拓展,5,6,1,5,37,3,4,3,4,1,5,2,5,+,+0.75,3,5,3,4,-,5,14,13,14,9,11,5,11,+,回顾,整数乘法的（）、（）和（）对于分数乘法同样适用。,交换律,结合律,分配律,17,应用（）计算比较简便。,5,8,4,5,乘法交换律,（）,24,应用（）计算比较简便。,1,12,1,8,乘法分配律,9,应用（）计算比较简便。,7,20,5,9,乘法结合律,（）,20=,20,20,应用了乘法结合律。（）,1,10,1,5,1,10,1,5,=,（）应用了乘法结合律。（）,1,3,1,4,2,3,1,3,1,4,2,3,9 =9,应用了乘法交换律。（）,5,8,4,55,8,4,5,两个真分数的积一定还是真分数。（）,大法官巧断案（对的打“”，错的打“”）,对号入座（将正确的答案的序号填在括号里）,加法与乘法比较，加法没有（）。,A.,交换律,B.,结合律,C.,分配律,98=9,（,8,）应用了乘法（）。,A.,交换律,B.,结合律,C.,分配律,D.,交换律和结合律,1,4,1,4,C,D,对号入座（将正确的答案的序号填在括号里）,计算,12,（）,=12,12,运用（）。,A.,乘法交换律,B.,乘法结合律,C.,乘法分配律,1,6,1,4,1,6,1,4,一个非零的自然数乘（），积不小于这个自然数。,A,、真分数,B,、假分数,C,、,1,C,B思考题,2009,2010,2011,2009,2009,2010,8,15,7,9,4,15,8,9,9,13,5,8,6,13,5,8,5,8,1,12,1,23,1,34,1,20052006,?,2009,2010,2011,（,2010,1,）,2009,2010,=,2010,1,2009,2010,=,2009,2010,2009,2010,=,2009,2009,2010,=,2009,2009,2010,2011,=,1,2010,（,1,）,2011,=,1,2010,12011,2011,=,2011,2010,2011,=,2010,2010,2010,1,1,2010,=,2009,2009,2010,=,（,2010,1,）,（）,2010,2010,1,2010,2009,2009,2010,（,2010,1,）,2009,2010,=,2010,1,2009,2010,=,2009,2010,2009,=,2009,2010,2009,2010,2008,=,2010,2010,2008,=,1,2010,2009,2009,2010,2009,（,1,）,1,2010,=,2009,1,2009,1,2010,=,2009,2009,2010,=,2008,2010,2010,=,2009,2010,2008,1,2010,=,8,15,7,9,4,15,8,9,15,9,8,7,4,15,8,9,=,4,15,8,9,=,（）,7,15,8,9,=,3,15,1,3,8,45,=,8,15,7,9,4,15,8,9,4,8,8,15,7,9,15,9,=,4,9,8,15,7,9,=,（）,8,15,3,9,=,1,3,8,45,=,9,13,5,8,6,13,5,8,5,8,9,13,5,8,6,13,=,1,5,8,5,8,9,13,6,13,=,（,1,）,5,8,5,8,3,13,=1,5,8,16,13,=,1,2,10,13,=,1,12,1,23,1,34,1,20052006,1,2,1,2,1,3,1,3,1,4,=,（,1-,）,+,（,-,）,+,（,-,）,+,1,2006,1,2005,1,2004,（,-,）,+,（,-,）,1,2005,1,2,1,2,1,3,1,3,1,4,=1-+-+-+-,1,2005,1,2004,+-,1,2006,1,2005,=1,1,2006,2005,2006,=,