1. 直接写出得数。
$\frac{1}{3}-\frac{2}{15}=$ $\frac{9}{16}-\frac{1}{4}=$ $\frac{6}{7}-\frac{8}{21}=$ $\frac{7}{11}-\frac{1}{3}+\frac{4}{11}=$
$\frac{7}{8}+\frac{1}{3}=$ $\frac{5}{6}+\frac{1}{4}=$ $\frac{1}{5}+\frac{9}{5}=$ $\frac{1}{5}+\frac{4}{5}-\frac{2}{5}=$
$\frac{5}{6}-\frac{3}{4}=$ $\frac{7}{10}-\frac{1}{10}=$ $\frac{11}{12}-\frac{1}{8}=$ $2-\frac{1}{4}+\frac{1}{4}=$
$\frac{1}{6}+\frac{1}{8}=$ $\frac{2}{3}+\frac{1}{6}=$ $\frac{1}{2}+\frac{5}{2}=$ $\frac{7}{15}-\frac{1}{5}-\frac{1}{15}=$
$\frac{1}{5}+\frac{6}{5}=$ $\frac{3}{7}+\frac{3}{7}=$ $\frac{9}{10}-\frac{2}{5}=$ $\frac{11}{12}-\frac{3}{10}+\frac{1}{12}=$
$\frac{1}{2}+\frac{1}{4}=$ $\frac{11}{4}-\frac{3}{4}=$ $\frac{5}{6}+\frac{1}{7}=$ $\frac{13}{10}+\frac{3}{10}-\frac{4}{5}=$

1. $\frac{1}{5}$ $\frac{5}{16}$ $\frac{10}{21}$ $\frac{2}{3}$
$\frac{29}{24}$ $\frac{13}{12}$ $2$ $\frac{3}{5}$
$\frac{1}{12}$ $\frac{3}{5}$ $\frac{19}{24}$ $2$
$\frac{7}{24}$ $\frac{5}{6}$ $3$ $\frac{1}{5}$
$\frac{7}{5}$ $\frac{6}{7}$ $\frac{1}{2}$ $\frac{7}{10}$
$\frac{3}{4}$ $2$ $\frac{41}{42}$ $\frac{4}{5}$

2. 计算下面各题，能简算的要简算。
$\frac{5}{6}-\frac{4}{9}+\frac{1}{6}-\frac{5}{9}$ $\frac{1}{9}+\frac{11}{12}-\frac{17}{36}$ $\frac{5}{4}-\frac{2}{7}-(\frac{1}{4}+\frac{3}{7})$
$\frac{13}{10}+\frac{3}{4}+\frac{7}{10}$ $8-\frac{17}{42}-\frac{25}{42}$ $\frac{9}{10}-(\frac{7}{15}-\frac{3}{20})$

2. $0$ $\frac{5}{9}$ $\frac{2}{7}$
$2\frac{3}{4}$ $7$ $\frac{7}{12}$

$\frac{9}{10}+\frac{99}{100}+\frac{999}{1000}+\frac{9999}{10000}+\frac{99999}{100000}$的结果的整数部分是几？

·思维提升
$\frac{9}{10}+\frac{99}{100}+\frac{999}{1000}+\frac{9999}{10000}+\frac{99999}{100000}$
$=1-\frac{1}{10}+1-\frac{1}{100}+1-\frac{1}{1000}+1-\frac{1}{10000}+1-\frac{1}{100000}$
$=1-0.1+1-0.01+1-0.001+1-0.0001+1-0.00001$
$=(1+1+1+1+1)-(0.1+0.01+0.001+0.0001+0.00001)$
$=5-0.11111$
$=4.88889$
这个算式的结果的整数部分是$4$。