一、口算。
$2^2 - 1^2 =$
$5.5 - 0.9 =$
$3.14×(7^2 - 3^2) =$
$3^2 - 2^2 =$
$8×1.25 =$
$3.14×(4^2 - 3^2) =$
$5^2 - 4^2 =$
$7.2÷0.08 =$
$3.14×(6^2 - 4^2) =$
$6^2 - 5^2 =$
$0.87 + 0.3 =$
$3.14×(0.6÷2)^2 =$
$7^2 - 6^2 =$
$488÷8 =$
$3.14×(60÷3)^2 =$
$8^2 - 5^2 =$
$2.4×0.5 =$
$3.14×(11^2 - 9^2) =$
$9^2 - 4^2 =$
$0.65÷1.3 =$
$3.14×(20÷2)^2 =$
$12^2 - 10^2 =$
$705×2 =$
$3.14×(14÷7)^2 =$

$2^2 - 1^2 = 3$
$5.5 - 0.9 = 4.6$
$3.14×(7^2 - 3^2) = 125.6$
$3^2 - 2^2 = 5$
$8×1.25 = 10$
$3.14×(4^2 - 3^2) = 21.98$
$5^2 - 4^2 = 9$
$7.2÷0.08 = 90$
$3.14×(6^2 - 4^2) = 62.8$
$6^2 - 5^2 = 11$
$0.87 + 0.3 = 1.17$
$3.14×(0.6÷2)^2 = 0.2826$
$7^2 - 6^2 = 13$
$488÷8 = 61$
$3.14×(60÷3)^2 = 1256$
$8^2 - 5^2 = 39$
$2.4×0.5 = 1.2$
$3.14×(11^2 - 9^2) = 125.6$
$9^2 - 4^2 = 65$
$0.65÷1.3 = 0.5$
$3.14×(20÷2)^2 = 314$
$12^2 - 10^2 = 44$
$705×2 = 1410$
$3.14×(14÷7)^2 = 12.56$

二、计算下面各图形中涂色部分的面积。
1.
2.

1. $3.14×(8^2 - 4^2)=150.72(\mathrm{dm}^2)$
2. $10×8 - 3.14×(8÷2)^2=29.76(\mathrm{cm}^2)$