1. 口算。(建议用时3分钟)
$3.5 - \frac{1}{2} =$
$\frac{8}{9} ÷ 4 =$
$\frac{3}{5} × 65 =$
$\frac{8}{9} × 75\% =$
$0.5 - 20\% =$
$\frac{5}{16} × \frac{4}{25} =$
$\frac{5}{8} × \frac{16}{25} =$
$\frac{5}{4} × 80\% =$
$\frac{1}{2} ÷ \frac{3}{4} =$
$3 - 195\% =$
$\frac{14}{45} × \frac{5}{21} =$
$\frac{8}{3} × \frac{1}{3} =$
$50 × (1 + 20\%) =$
$40 × 40\% × 10\% =$
$90 - 90 × 50\% =$
$24 + 24 × 20\% =$
$25 × (1 - 40\%) =$
$3.5 + 3.5 × 60\% =$

1. $3.5 - \frac{1}{2} = 3$
$\frac{8}{9} ÷ 4 = \frac{2}{9}$
$\frac{3}{5} × 65 = 39$
$\frac{8}{9} × 75\% = \frac{2}{3}$
$0.5 - 20\% = 0.3$
$\frac{5}{16} × \frac{4}{25} = \frac{1}{20}$
$\frac{5}{8} × \frac{16}{25} = \frac{2}{5}$
$\frac{5}{4} × 80\% = 1$
$\frac{1}{2} ÷ \frac{3}{4} = \frac{2}{3}$
$3 - 195\% = 1.05$
$\frac{14}{45} × \frac{5}{21} = \frac{2}{27}$
$\frac{8}{3} × \frac{1}{3} = \frac{8}{9}$
$50 × (1 + 20\%) = 60$
$40 × 40\% × 10\% = 1.6$
$90 - 90 × 50\% = 45$
$24 + 24 × 20\% = 28.8$
$25 × (1 - 40\%) = 15$
$3.5 + 3.5 × 60\% = 5.6$

2. 计算下面各题，能用简便算法的就用简便算法。（建议用时5分钟）
$\frac{1}{2}×101 - 0.5$
$130÷(\frac{1}{2}÷\frac{4}{5} + 1)$
$512×20×50\%$
$32÷25\%×125\%$
$600×(1 + 3.75\%×2)$
$400×40\%×(1 - 30\%)$

2. $\frac{1}{2}×101 - 0.5 = 50$
$130÷(\frac{1}{2}÷\frac{4}{5} + 1) = 80$
$512×20×50\% = 5120$
$32÷25\%×125\% = 160$
$600×(1 + 3.75\%×2) = 645$
$400×40\%×(1 - 30\%) = 112$

3. 解决问题。（建议用时2分钟）
“绿水青山就是金山银山。”为响应绿色发展的号召，桐林乡去年植树造林200公顷，今年计划植树造林比去年增加20%，实际植树造林比计划植树造林少10%。今年实际植树造林多少公顷？

3. $200 × (1 + 20\%) × (1 - 10\%) = 216$(公顷)