1. 计算下列图形的面积。
(1)
(2)
(3)
(4)

(1) $3.14×4^2=50.24(\mathrm{cm}^2)$
(2) $3.14×(\frac{10}{2})^2=78.5(\mathrm{cm}^2)$
(3) $12.56÷3.14÷2=2(\mathrm{dm})$
$3.14×2^2=12.56(\mathrm{dm}^2)$
(4) $3.14×(\frac{6}{2})^2÷2=14.13(\mathrm{cm}^2)$

2. 计算阴影部分的面积。
(1)
(2)
(3)
(4)

(1) $4×2=8(\mathrm{cm})$
$8×4-3.14×4^2÷2=6.88(\mathrm{cm}^2)$
(2) $10×8-3.14×(\frac{8}{2})^2=29.76(\mathrm{cm}^2)$
(3) $25×10+3.14×(\frac{10}{2})^2=328.5(\mathrm{m}^2)$
(4) $4×4-3.14×(\frac{4}{2})^2÷2=9.72(\mathrm{cm}^2)$