一 夺小旗。
开始→$\frac{2}{5}+\frac{2}{5}=$ → $\frac{7}{11}-\frac{4}{11}=$ → $\frac{7}{10}-\frac{1}{5}=$ → $\frac{2}{3}+\frac{1}{4}=$
↓
$\frac{5}{7}-\frac{3}{7}=$ ← $\frac{2}{5}-\frac{1}{4}=$ ← $4-3\frac{1}{2}=$ ← $\frac{1}{2}+\frac{3}{4}-\frac{1}{2}+\frac{1}{4}=$
↓
$1-\frac{3}{4}=$ → $1-\frac{1}{9}-\frac{1}{3}=$ → $\frac{3}{8}+\frac{1}{2}=$ → $\frac{8}{15}-\frac{1}{5}=$

$\frac{2}{5}+\frac{2}{5}=\frac{4}{5}$
$\frac{7}{11}-\frac{4}{11}=\frac{3}{11}$
$\frac{7}{10}-\frac{1}{5}=\frac{1}{2}$
$\frac{2}{3}+\frac{1}{4}=\frac{11}{12}$
$\frac{5}{7}-\frac{3}{7}=\frac{2}{7}$
$\frac{2}{5}-\frac{1}{4}=\frac{3}{20}$
$4-3\frac{1}{2}=\frac{1}{2}$
$\frac{1}{2}+\frac{3}{4}-\frac{1}{2}+\frac{1}{4}=1$
$1-\frac{3}{4}=\frac{1}{4}$
$1-\frac{1}{9}-\frac{1}{3}=\frac{5}{9}$
$\frac{3}{8}+\frac{1}{2}=\frac{7}{8}$
$\frac{8}{15}-\frac{1}{5}=\frac{1}{3}$

看图填一填，涂一涂。

算式: + =
算式: + =

算式: + =

算式: + =

$\frac{1}{2} + \frac{1}{4} = \frac{3}{4}$
$\frac{2}{5} + \frac{3}{5} = 1$
$\frac{1}{4} + \frac{3}{8} = \frac{5}{8}$
$\frac{1}{2} + \frac{1}{3} = \frac{5}{6}$
答：四个算式的计算结果如上，第三个图形分别对应将结果对应的份数涂色即可。

三 连一连,下面算式的结果各等于或接近几?
1 $\frac{1}{2}$ 0
$\frac{1}{2}+\frac{11}{22}$ $\frac{2}{3}+\frac{3}{8}$ $\frac{5}{7}-\frac{4}{21}$ $\frac{1}{19}-\frac{1}{20}$
$2-\frac{24}{25}$ $\frac{3}{4}-\frac{7}{32}$ $\frac{2}{9}+\frac{1}{3}$ $1-\frac{12}{25}$ $1-\frac{18}{19}$

$\frac{1}{2}+\frac{11}{22}=1$
$\frac{2}{3}+\frac{3}{8}=\frac{25}{24}\approx1$
$2-\frac{24}{25}=\frac{26}{25}\approx1$
$\frac{17}{36}+\frac{1}{12}=\frac{5}{9}\approx\frac{1}{2}$
$\frac{5}{7}-\frac{4}{21}=\frac{11}{21}\approx\frac{1}{2}$
$\frac{3}{4}-\frac{7}{32}=\frac{17}{32}\approx\frac{1}{2}$
$\frac{2}{9}+\frac{1}{3}=\frac{5}{9}\approx\frac{1}{2}$
$1-\frac{12}{25}=\frac{13}{25}\approx\frac{1}{2}$
$\frac{1}{19}-\frac{1}{20}=\frac{1}{380}\approx0$
$1-\frac{18}{19}=\frac{1}{19}\approx0$
答：
和1相连的算式：$\frac{1}{2}+\frac{11}{22}$、$\frac{2}{3}+\frac{3}{8}$、$2-\frac{24}{25}$
和$\frac{1}{2}$相连的算式：$\frac{17}{36}+\frac{1}{12}$、$\frac{5}{7}-\frac{4}{21}$、$\frac{3}{4}-\frac{7}{32}$、$\frac{2}{9}+\frac{1}{3}$、$1-\frac{12}{25}$
和0相连的算式：$\frac{1}{19}-\frac{1}{20}$、$1-\frac{18}{19}$。