铁王乡中心小学 设计与执教:贠伟涛
DESCRIPTION
约分. 铁王乡中心小学 设计与执教:贠伟涛. 复习 : 求下面各组数的最大公因数 : 28 和 42 18 和 6 5 和 13. 18 9 3 尝试比较 : ------ ------ ------ 的大小 . 24 ` 12 ` 4. 18 9 3 尝试比较 : ------ ------ ------ 的大小 . - PowerPoint PPT PresentationTRANSCRIPT
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铁王乡中心小学 设计与执教:贠伟涛
![Page 2: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/2.jpg)
复习 :
求下面各组数的最大公因数 :
28 和 42 18 和 6 5 和 13
![Page 3: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/3.jpg)
18 9 3 尝试比较 : ------ ------ ------ 的大小 . 24 ` 12 ` 4
![Page 4: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/4.jpg)
18 9 3 尝试比较 : ------ ------ ------ 的大小 . 24 ` 12 ` 4
![Page 5: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/5.jpg)
18 9 3 尝试比较 : ------ ------ ------ 的大小 . 24 ` 12 ` 4
![Page 6: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/6.jpg)
18 9 3 尝试比较 : ------ ------ ------ 的大小 . 24 ` 12 ` 4
![Page 7: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/7.jpg)
18 9 3 尝试比较 : ------ ------ ------ 的大小 . 24 ` 12 ` 4
= =
![Page 8: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/8.jpg)
把一个分数的分子、分母同时除以公因数,分数的值不变,这个过程叫做
约分
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例: = = =
不能约分,这样的分数叫做最简分数
![Page 10: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/10.jpg)
牛刀小试
把 化成最简分数
![Page 11: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/11.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 6 3 8 5 15 --- --- --- --- --- --- 7 9 10 10 12 40
![Page 12: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/12.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 6 3 8 5 15 --- --- --- --- --- --- 7 9 10 10 12 40
是
![Page 13: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/13.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 6 3 8 5 15 --- --- --- --- --- --- 7 9 10 10 12 40
是 是
![Page 14: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/14.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 6 3 8 5 15 --- --- --- --- --- --- 7 9 10 10 12 40
是 是 是
![Page 15: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/15.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 2 3 8 5 15 --- --- --- --- --- --- 7 3 10 10 12 40
是 是 是
![Page 16: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/16.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 2 3 4 5 15 --- --- --- --- --- --- 7 3 10 5 12 40
是 是 是
![Page 17: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/17.jpg)
尝试练习 : 指出下面哪些分数是最简分数
4 2 3 4 5 3 --- --- --- --- --- --- 7 3 10 5 12 8
是 是 是
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1212 把 把 ----- ----- 约分 约分 30 30
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把下面的分数约分 ( 口答 ) 4 9 8 12 33 --- --- --- --- --- 6 12 32 16 55
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把下面的分数约分 : 2 9 8 12 33 --- --- --- --- --- 3 12 32 16 55
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把下面的分数约分 : 2 3 8 12 33 --- --- --- --- --- 3 4 32 16 55
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把下面的分数约分 : 2 3 1 12 33 --- --- --- --- --- 3 4 4 16 55
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把下面的分数约分 : 2 3 1 3 33 --- --- --- --- --- 3 4 4 4 55
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把下面的分数约分 : 2 3 1 3 3 --- --- --- --- --- 3 4 4 4 5
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练习1:
把下面的分数约分(看谁做得又对又快)
5 9 20 14 22 40--- --- --- --- --- ---10 15 25 35 77 70
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练习1:
把下面的分数约分(看谁做得又对又快)
1 9 20 14 22 40--- --- --- --- --- --- 2 15 25 35 77 70
![Page 27: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/27.jpg)
练习1:
把下面的分数约分(看谁做得又对又快)
1 3 20 14 22 40--- --- --- --- --- --- 2 5 25 35 77 70
![Page 28: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/28.jpg)
练习1:
把下面的分数约分(看谁做得又对又快)
1 3 4 14 22 40--- --- --- --- --- --- 2 5 5 35 77 70
![Page 29: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/29.jpg)
练习1:
把下面的分数约分(看谁做得又对又快)
1 3 4 2 22 40--- --- --- --- --- --- 2 5 5 5 77 70
![Page 30: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/30.jpg)
练习1:
把下面的分数约分(看谁做得又对又快)
1 3 4 2 2 40--- --- --- --- --- --- 2 5 5 5 7 70
![Page 31: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/31.jpg)
练习1:
把下面的分数约分(看谁做得又对又快)
1 3 4 2 2 4--- --- --- --- --- --- 2 5 5 5 7 7
![Page 32: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/32.jpg)
练习 2 :
判断下面哪些分数没有约成最简分数
12 6 15 5(1) --- = --- ( ) (2) --- = --- ( ) 18 9 36 12
28 14 (3) --- = --- ( ) 42 21
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练习 2 :
判断下面哪些分数没有约成最简分数
12 6 15 5(1) --- = --- (×) (2) --- = --- ( ) 18 9 36 12
28 14 (3) --- = --- ( ) 42 21
![Page 34: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/34.jpg)
练习 2 :
判断下面哪些分数没有约成最简分数
12 6 15 5(1) --- = --- (×) (2) --- = --- (∨) 18 9 36 12 28 14 (3) --- = --- ( ) 42 21
![Page 35: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/35.jpg)
练习 2 :
判断下面哪些分数没有约成最简分数
12 6 15 5(1) --- = --- (×) (2) --- = --- (∨) 18 9 36 12 28 14 (3) --- = --- (×) 42 21
![Page 36: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/36.jpg)
练习 3 :
下面的约分对吗 ? 把不对的改正过来 .
15 3 45 3(1) --- = --- ( ) (2) --- = --- ( ) 24 4 75 5
2 2 (3) --- = --- ( ) 18 9
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练习 3 :
下面的约分对吗 ? 把不对的改正过来 .
15 3 45 3(1) --- = --- (×) (2) ---- = --- ( ) 24 4 75 5
2 2 (3) --- = --- ( ) 18 9
![Page 38: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/38.jpg)
练习 3 :
下面的约分对吗 ? 把不对的改正过来 .
15 3 45 3(1) --- = --- (×) (2) ---- = --- (∨ ) 24 4 75 5
2 2 (3) --- = --- ( ) 18 9
![Page 39: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/39.jpg)
练习 3 :
下面的约分对吗 ? 把不对的改正过来 .
15 3 45 3(1) --- = --- (×) (2) ---- = --- (∨ ) 24 4 75 5
2 2 (3) --- = --- (×) 18 9
![Page 40: 铁王乡中心小学 设计与执教:贠伟涛](https://reader030.vdocuments.site/reader030/viewer/2022033010/56814f5c550346895dbd0cd8/html5/thumbnails/40.jpg)