约分-(2).pptx

状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,人教,2001,课标版小学五年级数学下册,凉州区吴家井镇九年制学校：雷晓英,约 分,情景导入,复习旧知,在括号里填上适当的数，根据什么填的？,（）,=,4,（）,=,1,5,（）,=,3,2,4,根据分数的基本性质：分数的分子和分母同时乘或除以相同的数（,0,除外），分数的大小不变。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,填空,16,32,（）,16,4,（）,=,=,=,（）,4,1,（）,=,（）,9,10,（）,=,=,（）,24,20,（）,=,=,2,3,8,8,2,2,6,15,16,30,自主探究,把 化成分子和分母,比较小,且分数,大小不变,的分数。,24,30,你是怎么考虑的？,利用分数的基本性质。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,可以用分子和分母的公因数（,1,除外）去除。,24,30,=,242,302,=,12,15,12,15,=,123,153,=,4,5,想,想,一,有没有更简单的方法？,24,30,=,242,302,=,12,15,12,15,=,123,153,=,4,5,观察这两个式子，你发现了什么？,24,和,30,的最大公因数是,6,，除数的积是,24,和,30,的最大公因数。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,那我们直接用最大公因数做除数是不是更简单？,24,30,=,24,（）,30,（）,=,（）,（）,4,5,6,6,像这样，把一个分数化成和它相等，但分子和分母都比较小的分数，叫做,约分,。,24,30,=,4,5,12,15,4,5,或者,24,30,=,4,5,4,5,约分时也可以这样写：,4,5,的分子和分母只有公因数,1,。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,像,这样，分子和分母只有公因数,1,的分数叫做最简分数。,4,5,约分时，通常要约成最简分数。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,做,一,做,9,9,4,2,4,1,3,5,1,、下列分数中哪些是最简分数？把不是最简分数的化为最简分数。,、,、,、,、,是最简分数。,2,、把上下两行相等的两个分数用线连起来。,4,6,3,7,2,5,6,8,3,9,9,21,3,4,1,3,2,3,10,25,3,.,把下面各分数化成最简分数。,9,12,10,15,10,15,=,10,（）,15,（）,=,（,）,（）,2,3,5,5,9,（,）,12,（,）,9,12,=,=,（）,（）,3,4,3,3,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,今天，你收获了什么？,1.,完成,P66,页第,1,2,题；,2.,完成练习册本课时的习题。,课后作业,