你知道吗？计算工具的演变.ppt

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,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,小数的加法和减法,第1课时 小数加减法（1）,R四年级下册,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,计算时要注意什么？,4367+3205= 8754-5639=,7572,3115,相同数位对齐，从个位算起,算一算,导入新课,状元成才路,状元成才路,状元

2、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,小丽买了两本书，你知道她要付多少钱吗？,今天我们就来学习小数加减法。,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,自主探究,（1）小丽买了下面两本书，一共花了多少钱？,你知道了什么信息？用什么方法计算呢？,用加法计算。,6.45 + 4.29 =,+,7,4,1 0,4 . 2 9,1,

3、.,6 . 4 5,10.74（元）,十分位,百分位,个 位,答：一共花了10.74元。,相同数位上的两个数才能相加、减。,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,为什么小数点一定要对齐呢？,小数点对齐其实是为了让相同数位对齐。,原来小数加法与整数加法是一样的！,那么，小数减法也与整数减法一样吗？,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

4、成才路,状元成才路,状元成才路,状元成才路,（2）数学家的故事比童话选贵多少钱？,已知什么？求什么？,该用什么方法计算呢？,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,6.45 - 4.29,-,1,6,2,4 . 2 9,.,.,6 . 4 5,2.16（元）,答：数学家的故事比童话选贵2.16元。,你会算了吗？,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

5、元成才路,状元成才路,状元成才路,状元成才路,状元成才路,计算小数加、减法时要注意什么呢？,（1）相同数位对齐； （2）从末位算起，加法要注意哪一位相加满十，要向前一位进1；减法要注意哪位不够减要从前一位退1当10在本位上加10再减； （3）得数的小数点要与竖式中的小数点对齐。,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,1.计算下面各题，并且验算。,怎么验算呢？,=3.54,=17.2,=10.96,=3.86,=6.4,=8.16,加、减法是互

6、逆运算，可以用这个检验！,你算对了吗？,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,4,2.98+0.56=,12.53+4.67=,3.54,17.2,验算：,验算：,1.计算下面各题，并且验算。,1,5,1,.,3,0,1,2,1,.,7,1,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,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,6.07+4

7、.89=,5.64-1.78=,10.96,3.86,验算：,验算：,6,1,9,.,1 0,.,6,.,8,.,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,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,7.2-0.8=,15.62-7.46=,6.4,8.16,验算：,验算：,.,4,.,6,.,6,1,.,.,8,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

8、才路,状元成才路,（1）小明从7岁到10岁，体重增加了多少千克？,答：体重增加了7.1千克。,2.下面是小明的体重统计图。,29.822.7=,7.1（千克）,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,（2）哪一年比上一年增加得最多？增加了多少？,24.622.71.9（千克）,27.524.62.9（千克）,29.827.52.3（千克）,2.9千克2.3千克1.9千克,答：9岁那年比上一年增加得最多，增加了2.9千克。,状元成才路,状元成才路

9、,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,巩固深化,1.小刚身高1.37米，比小虎矮0.05米，小虎的身高是多少米？,1.37+0.051.42（米）,答：小虎的身高是1.42米。,用什么方法计算？,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,2.羊村长病了，喜羊羊带着10元钱去给村长买药，应该找回多少钱？,花了0.8元。

10、,10.0,- 0.8,9.2,答：应该找回9.2元。,10 0.8 =_（元）,9.2,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,3.,0.95-0.35=0.6（千克）,杯里的水有多少千克？,答：杯里的水有0.6千克？,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,课堂小结,6.45+4.29=10.74,6.45 - 4.29=2.16,小数加减法在意义上、计算方法上和整数加减法是一样的。,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