《人教版五年级数学上册第一单元之《小数乘小数(3)》(例5)课件.pptx》由会员分享，可在线阅读，更多相关《人教版五年级数学上册第一单元之《小数乘小数(3)》(例5)课件.pptx（16页珍藏版）》请在三一办公上搜索。
1、第一单元 小数乘法,小数乘小数（例5）,课本第7页 例5,鸵鸟的最高速度是非洲野狗的1.3倍，鸵鸟的最高速度是,561.3 =,多少千米/时？,561.3 =,7.28,5,6,.,3,6,8,1,5,6,2,8,7,.,1,请验算一下！,可以怎样进行验算呢？,1,3,.,6,7,8,5,6,5,2,8,7,.,561.3 =,72.8,561.3 =,7.28,5,6,.,3,6,8,1,5,6,2,8,7,.,1,72.8,课本第7页 做一做,下面各题计算得对吗？把不对的改正过来。,3.22.5 = 0.8,2.61.08 = 2.708,3,2,.,5,6,0,2,6,4,0,0,8,.
2、,.,1,8,0,8,.,6,4,8,2,1,6,0,8,8,.,1,6,2,2,.,2.808,3. 判断下面各个积的小数位数有没有错误。,课本第8页 练习二,56.738 = 2154.6,2.85.6 = 1.568,0.370.94 = 3.478,1.2329.2 = 359.16,1.560.9 = 1.404,0.786.1 = 47.58,1位,1位,2位,3位,4位,3位,3位,2位,3位,3位,3位,2位,注：当两个因数末位相乘是整十数时（如56 = 30，58 = 40），此方法不合适，可能要算一算了。,6. 先计算，再验算。,课本第9页 练习二,0.392.9 =,3,
3、9,.,9,5,1,2,7,8,3,1,1,.,0,3,1,.,1.131,验算：,2,9,.,9,6,1,3,8,7,3,1,1,.,0,2,1,.,0.580.08 =,5,8,.,8,6,4,0,.,0,4,0,.,0.0464,验算：,0,8,.,8,6,4,5,4,0,6,4,4,0,0,.,0,0,0,.,0,3,7,.,0,4,0,7,.,2,0,0,3.7200 =,740,2,0,.,1,4,7,6,4,0,7,.,3,0,0,验算：,0.188.45 =,1.521,1,8,.,5,9,0,4,7,2,0,8,.,4,1,0,2,.,4,5,1,1,4,5,.,8,6,0,
4、1,4,5,1,0,2,.,8,7,8,5,0,.,6,1,验算：,4.50.002 =,0.009,4,5,.,2,9,0,0,.,0,0,.,0,0,0,0,2,.,5,1,0,4,8,9,0,0,.,0,0,.,0,0,验算：,0.0720.15 =,0.0108,7,2,.,5,6,0,1,2,8,0,0,.,0,1,.,0,0,0,3,7,0,验算：,1,5,.,2,3,0,7,5,8,0,0,.,0,1,.,0,0,0,0,0,1,5. 地球直径1.28万千米，月球到地球的距离是地球直径的30倍。,1.2830,答：月球到地球的距离有38.4万千米。,= 38.4（万千米）,课本第
5、8页 练习二,月球到地球有多远？,7. 世界上最大的一棵巨杉，质量是蓝鲸的18.7倍，高是蓝鲸体长,课本第9页 练习二,哇，好大的树洞，可以通过一辆汽车！,体重150吨，体长25.9m。,巨杉的质量：,巨杉的高度：,15018.7 =,2805（t）,25.93.2 =,82.88（m）,答：这棵巨杉重2805t，高82.88m。,的3.2倍。这棵巨杉重多少吨？高多少米？,8. 一只梅花鹿高1.46m，一只长颈鹿的高度是梅花鹿的3.5倍。,课本第9页 练习二,梅花鹿比长颈鹿矮多少米？,1.463.5 =,5.11（m）,5.11 - 1.46 =,3.65（m）,答：长颈鹿高5.11m，梅花鹿比长颈鹿矮3.65m。,这只长颈鹿高多少米？,
