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# æ§æï¼è¥¿åç¬¬åäºå°å­¦ æç«å° - PowerPoint PPT Presentation

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## PowerPoint Slideshow about 'æ§æï¼è¥¿åç¬¬åäºå°å­¦ æç«å°' - kieran-west

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• 两个图形用同样的方法和速度涂完颜色,
• 哪个用的时间长?
• 为什么?

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1、在转化的过程中，什么变了？什么没变？

2、近似平行四边形的底与圆的周长有什么关系？

3、近似平行四边形的高与圆的半径有什么关系？

20÷2=10（m）

3.14×102 =3.14×100 =314（m2）

.

40m

.

2

3.14 ×5

5cm

2

3.14×20

2

=78.5（cm ）

2

=1256（m）

40÷2=20（m）

=3.14 ×25

=3.14 ×400

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3

2

10

2

5

2

7

2

20

=

25

=

9

=

100

=

49

400

=

3.14×22

=3.14×4

=12.56（平方米）

3.14×32

=3.14×9

=28.26（平方米）

3.14×152

=3.14×225

=706.5（平方米）

60m

100m

3.14×302

=3.14×900

=2826（m2）

60÷2=30（m）

60×100=6000 （m2）

2826+6000=8826（m2）