1. 直接写出得数。
$\frac{1}{3}+\frac{1}{4}=$ $\frac{3}{5}-\frac{1}{3}=$ $\frac{1}{3}+\frac{1}{6}=$ $\frac{2}{7}+\frac{3}{14}=$ $\frac{7}{12}+\frac{1}{12}=$
$1-\frac{5}{18}=$ $\frac{7}{9}+\frac{11}{9}=$ $\frac{1}{5}-\frac{1}{6}=$ $\frac{3}{8}+\frac{5}{8}=$ $\frac{5}{9}-\frac{2}{9}=$

$\frac{1}{3}+\frac{1}{4}=\frac{7}{12}$
$\frac{3}{5}-\frac{1}{3}=\frac{4}{15}$
$\frac{1}{3}+\frac{1}{6}=\frac{1}{2}$
$\frac{2}{7}+\frac{3}{14}=\frac{1}{2}$
$\frac{7}{12}+\frac{1}{12}=\frac{2}{3}$
$1-\frac{5}{18}=\frac{13}{18}$
$\frac{7}{9}+\frac{11}{9}=2$
$\frac{1}{5}-\frac{1}{6}=\frac{1}{30}$
$\frac{3}{8}+\frac{5}{8}=1$
$\frac{5}{9}-\frac{2}{9}=\frac{1}{3}$

2. 计算下面各题,能简算的要简算。
$1-(\dfrac{2}{3}-\dfrac{1}{2})$
$\dfrac{7}{8}-\dfrac{5}{12}+\dfrac{1}{6}$
$\dfrac{7}{8}-(\dfrac{3}{10}+\dfrac{1}{4})$
$\dfrac{9}{11}-\dfrac{5}{7}+\dfrac{2}{11}-\dfrac{2}{7}$

$1-(\dfrac{2}{3}-\dfrac{1}{2})$
$=1-(\dfrac{4}{6}-\dfrac{3}{6})$
$=1-\dfrac{1}{6}$
$=\dfrac{5}{6}$
$\dfrac{7}{8}-\dfrac{5}{12}+\dfrac{1}{6}$
$=\dfrac{21}{24}-\dfrac{10}{24}+\dfrac{4}{24}$
$=\dfrac{15}{24}$
$=\dfrac{5}{8}$
$\dfrac{7}{8}-(\dfrac{3}{10}+\dfrac{1}{4})$
$=\dfrac{7}{8}-(\dfrac{6}{20}+\dfrac{5}{20})$
$=\dfrac{7}{8}-\dfrac{11}{20}$
$=\dfrac{35}{40}-\dfrac{22}{40}$
$=\dfrac{13}{40}$
$\dfrac{9}{11}-\dfrac{5}{7}+\dfrac{2}{11}-\dfrac{2}{7}$
$=(\dfrac{9}{11}+\dfrac{2}{11})-(\dfrac{5}{7}+\dfrac{2}{7})$
$=1-1$
$=0$

1. 欢欢用一张长方形彩纸的$\frac{2}{5}$折了一艘小船，乐乐用一张同样大小的长方形彩纸的$\frac{3}{4}$折了一架飞机。欢欢和乐乐合用一张彩纸，够吗？

$\frac{2}{5}+\frac{3}{4}$
$=\frac{8}{20}+\frac{15}{20}$
$=\frac{23}{20}$
$\frac{23}{20}＞1$
答：欢欢和乐乐合用一张彩纸，不够。

2. 小华用5元买了一张$\frac{3}{5}$ m²的卡纸，小华做贺卡用去了这张卡纸的$\frac{1}{10}$，做手工又用去了这张卡纸的$\frac{1}{3}$，？请在横线上提出一个数学问题并解答。

两次一共用去这张卡纸的几分之几？
$\frac{1}{10}+\frac{1}{3}=\frac{3}{30}+\frac{10}{30}=\frac{13}{30}$
答：两次一共用去这张卡纸的$\frac{13}{30}$。