小学数学人教版四年级下册教学1单元四则运算2课时乘除法的意义和各部分间的关系

四则运算1www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com优翼第2课时乘、除法的意义和各部分间的关系义务教育人教版四年级下册 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com还记得加、减法的意义和各部分间的关系吗？和=加数+加数加数=和-另一个加数差=被减数-减数减数=被减数-差被减数=减数+差复习导入一 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com（1）每个花瓶里插3枝花，4个花瓶一共插了多少枝花？用加法算：3+3+3+3＝12用乘法算：3×4＝12求几个相同加数的和的简便运算，叫做乘法。2探究新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com乘法算式各部分名称：3×4＝12因数因数积探究新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com（2）有12枝花，每3枝插一瓶，可以插几瓶？（3）有12枝花，平均插到4个花瓶里，每个花瓶插几枝？12÷3=412÷4=3探究新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com（2）有12枝花，每3枝插一瓶，可以插几瓶？12÷3=4（3）有12枝花，平均插到4个花瓶里，每个花瓶插几枝？12÷4=3（1）每个花瓶里插3枝花，4个花瓶一共插了多少枝花？3×4＝12与第（1）相比，第（2）、（3）题分别是已知什么？求什么？怎样算？探究新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com已知两个数的积和一个因数,求另一个因数,用除法计算。探究新知二 问题：用你自己的话说一说，你认为什么是除法？除法算式中各部分的名称是什么？除法是已知两个因数的积与其中一个因数，求另一个因数的运算。在除法中，已知的积叫做被除数。探究新知二 问题：说一说除法和乘法有什么关系？除法是乘法的逆运算。探究新知二 1.乘法各部分间的关系。小组讨论积=因数×因数因数=积÷另一个因数探究新知二 2.除法各部分间的关系。小组讨论商=被除数÷除数除数=被除数÷商被除数=商×除数探究新知二 3.想一想：在有余数的除法里，被除数与商、除数和余数之间有什么关系？小组讨论被除数＝商×除数＋余数探究新知二 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com问题：你是根据什么得出结果的？3614根据36×14＝504，直接写出下面两道题的得数。504÷14＝504÷36＝根据乘除法之间的关系得出结果。教材做一做优翼巩固练习三 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com1.四年级有4个班，每班40人，一共有多少人？40×4=160（人）2.四年级有160人，平均分成4个班，每班多少人？160÷4=40（人）3.四年级有160人，每40人分一班，可分成几个班？160÷40=4（个）巩固练习三 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com4.水果店运来20筐苹果，共500千克。平均每筐苹果有多少千克？500÷20=25（千克）5.光明小学有2400本图书。图书的本数正好是学生人数的4倍。光明小学有多少名学生？2400÷4=600（名）巩固练习三 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com乘法各部分间的关系：积=因数×因数因数=积÷另一个因数除法各部分间的关系：商=被除数÷除数除数=被除数÷商被除数=商×除数课堂小结四 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com乘法除法除法除法理由略教材P7T1优翼课后练习五 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com13936÷208=6713936÷67=2081125÷45=2545×25=11251008÷21=4848×21=1008教材P7T2优翼课后练习五 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com42843700教材P7T3优翼课后练习五 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com101542036教材P7T4优翼课后练习五 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com48×27=102×85=754÷29=876÷73=129686702612验算略教材P7T5优翼课后练习五 www.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.comwww.youyi100.com6×12+3=75（个）教材P8T6优翼课后练习五