《2025年口算训练六年级数学上册人教版双色升级版》

7π =
10π =
4π =
2π =
9π =
5π =
8π =
20π =
3π =
6π =
$9^2 = $
$10^2 = $
$4^2 = $
$7^2 = $
$5^2 = $
$8^2 = $
$3^2 = $
$6^2 = $
$12^2 = $
$15^2 = $
$18^2 =$

答案： 21.98
31.4
12.56
6.28
28.26
15.7
25.12
62.8
9.42
18.84
81
100
16
49
25
64
9
36
144
225
324

$r = 1 m,C = (6.28)m,S = (3.14)m^2。$
$r = 3 cm,C = (18.84)cm,S = (28.26)cm^2。$
$d = 4 dm,C = (12.56)dm,S = (12.56)dm^2。$
$d = 20 cm,C = (62.8)cm,S = (314)cm^2。$
$d = 6 m,C = (18.84)m,S = (28.26)m^2。$
$r = 10 dm,C = (62.8)dm,S = (314)dm^2。$
$r = 2 m,C = (12.56)m,S = (12.56)m^2。$
C = 3.14 m,r = (0.5)m,d = (1)m。
$C = 6.28 cm,d = (2)cm,S = (3.14)cm^2。$
$C = 12.56 dm,d = (4)dm,S = (12.56)dm^2。$

答案： 答案：
$r = 1 m$
$C = 2\pi × 1 = 6.28 (m)$
$S = \pi × 1^2 = 3.14 (m^2)$
$r = 3 cm$
$C = 2\pi × 3 = 18.84 (cm)$
$S = \pi × 3^2 = 28.26 (cm^2)$
$d = 4 dm$
$C = \pi × 4 = 12.56 (dm)$
$S = \pi × (\frac{4}{2})^2 = 12.56 (dm^2)$
$d = 20 cm$
$C = \pi × 20 = 62.8 (cm)$
$S = \pi × (\frac{20}{2})^2 = 314 (cm^2)$
$d = 6 m$
$C = \pi × 6 = 18.84 (m)$
$S = \pi × (\frac{6}{2})^2 = 28.26 (m^2)$
$r = 10 dm$
$C = 2\pi × 10 = 62.8 (dm)$
$S = \pi × 10^2 = 314 (dm^2)$
$r = 2 m$
$C = 2\pi × 2 = 12.56 (m)$
$S = \pi × 2^2 = 12.56 (m^2)$
$C = 3.14 m$
$r = \frac{3.14}{2\pi} = 0.5 (m)$
$d = \frac{3.14}{\pi} = 1 (m)$
$C = 6.28 cm$
$d = \frac{6.28}{\pi} = 2 (cm)$
$S = \pi × (\frac{2}{2})^2 = 3.14 (cm^2)$
$C = 12.56 dm$
$d = \frac{12.56}{\pi} = 4 (dm)$
$S = \pi × (\frac{4}{2})^2 = 12.56 (dm^2)$