人教版小学数学六年级第四单元圆的练习题，要算式。有题目，求答案！在线等!

(12*12-10*12)*3.14
==44*3.14
=138.16cm^2

12/2=5cm
8/2=4cm
(5*5-4*4)*3.14
=9*3.14
=28.26cm^2

50+2=52cm
(52*52+50*50)*3.14
=204*3.14
=540.56cm^2

10/2=5cm
5*5*3.14=78.5cm^2
10*12-7805
=120-78.5
=41.5cm^2

2*2*3.14/2
=12.56/2
=6.28cm^2
(6.28-2.28)*2/4
=4*2/4
2cm

用大圆面积减小圆面积 即π10^2-π（10-2）^2

1、(12*12-10*12)*3.14
==44*3.14
=138.16cm^2

2、12/2=5cm
8/2=4cm
(5*5-4*4)*3.14
=9*3.14
=28.26cm^2

3、50+2=52cm
(52*52+50*50)*3.14
=204*3.14
=540.56cm^2

4、10/2=5cm
5*5*3.14=78.5cm^2
10*12-7805
=120-78.5
=41.5cm^2

5、2*2*3.14/2
=12.56/2
=6.28cm^2
(6.28-2.28)*2/4
=4*2/4
2cm