④某邮政运货车的车厢是长方体，从里面量长3 m，宽2.2 m，高2 m。它的容积是多少立方米？

$3×2.2×2=13.2$（立方米）
答：它的容积是13.2立方米。

计算下面各题。
(1)$\frac{1}{2022} + \frac{2}{2022} + \frac{3}{2022} + \dots + \frac{2020}{2022} + \frac{2021}{2022}$
(2)$1 + \frac{1}{2} - \frac{5}{6} + \frac{7}{12} - \frac{9}{20} + \frac{11}{30} - \frac{13}{42}$
(3)$\frac{1}{1 × 2} + \frac{1}{2 × 3} + \frac{1}{3 × 4} + \dots + \frac{1}{9 × 10}$

(1)
$\begin{aligned}&\frac{1}{2022} + \frac{2}{2022} + \frac{3}{2022} + \dots + \frac{2021}{2022}\\=&\frac{1+2+3+\dots+2021}{2022}\\=&\frac{(1+2021)×2021÷2}{2022}\\=&\frac{2022×2021÷2}{2022}\\=&\frac{2021}{2}\\=&1010\frac{1}{2}\end{aligned}$
(2)
$\begin{aligned}&1 + \frac{1}{2} - \frac{5}{6} + \frac{7}{12} - \frac{9}{20} + \frac{11}{30} - \frac{13}{42}\\=&1 + \frac{1}{2} - (\frac{1}{2}+\frac{1}{3}) + (\frac{1}{3}+\frac{1}{4}) - (\frac{1}{4}+\frac{1}{5}) + (\frac{1}{5}+\frac{1}{6}) - (\frac{1}{6}+\frac{1}{7})\\=&1 + \frac{1}{2} - \frac{1}{2} - \frac{1}{3} + \frac{1}{3} + \frac{1}{4} - \frac{1}{4} - \frac{1}{5} + \frac{1}{5} + \frac{1}{6} - \frac{1}{6} - \frac{1}{7}\\=&1 - \frac{1}{7}\\=&\frac{6}{7}\end{aligned}$
(3)
$\begin{aligned}&\frac{1}{1×2} + \frac{1}{2×3} + \frac{1}{3×4} + \dots + \frac{1}{9×10}\\=&1 - \frac{1}{2} + \frac{1}{2} - \frac{1}{3} + \frac{1}{3} - \frac{1}{4} + \dots + \frac{1}{9} - \frac{1}{10}\\=&1 - \frac{1}{10}\\=&\frac{9}{10}\end{aligned}$