小数的加法和减法.ppt

状元成才路,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,第2课时小数加减法（2）,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,算一算,导入新课,4.85+1.95=7.85-5.68=7.32+2.45=5.92-4.39=,6.8,2.17,9.77,1.53,今天我们继续学习小数加减法。,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,（1）小林买了下面两本书，一共花了多少钱？,自主探究,你知道了什么信息？用什么方法计算呢？,用加法计算。,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,百分位怎样加？,6.45+8.3=,我是这样做的。,这种做法对吗？为什么？,不对，小数点应该对齐，相同数位相加。,状元成才路,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,+,7,5,14,8.3,.,6.45,0,14.75（元）,答：一共花了14.75元。,6.45+8.3,可根据小数的性质，在百分位上添“0”再计算。,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,小数加减法与整数加减法有什么不同？,整数加减法要求末尾对齐，而小数加减法要小数点对齐。,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,已知什么？求什么？,该用什么方法计算呢？,（2）数学家的故事比神奇的大自然便宜多少钱？,状元成才路,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,8.3-6.45,8,5,1,.,.,1.85（元）,答：数学家的故事比神奇的大自然便宜1.85元。,.,0,百分位怎样减？,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,计算不同位数的小数加减法要注意什么？,小数点要对齐。,也就是把相同数位对齐。,当小数部分位数不同时，可以根据需要在末尾添“0”后再计算。,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,12+0.5=,12.56+5.8=,12.5,18.36,验算：,验算：,计算下面各题，并且验算。,5,.,12,6,3,1,.,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,113.04+7.8=,27-0.8=,120.84,26.2,验算：,验算：,4,8,.,0,1,2,1,.,2,6,.,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,16.4-3.2=,0.3-0.18=,13.2,0.12,验算：,验算：,2,.,3,1,.,2,1,.,0,状元成才路,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,巩固深化,17（元）,1.,8.648.36,玫瑰花8.64元/枝,向日葵8.36元/枝,月季花5.94元/枝,（1）玫瑰花和向日葵各买一枝，一共要花多少钱？,状元成才路,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,2.7（元）,8.645.94,1.,玫瑰花8.64元/枝,向日葵8.36元/枝,月季花5.94元/枝,(2)一枝月季花比一枝玫瑰花，便宜多少钱？,状元成才路,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.完成课本P74页第5题。,10.32,16.08,20.24,3.08,44.3,0.45,状元成才路,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.小明带了100元到文具店买文具，花了83.25元，还剩多少元？,100-83.25=16.75（元）,答：还剩16.75元。,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,课堂小结,状元成才路,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,