1. 填数。

$\begin{array}{ccc}\boxed{\dfrac{5}{8}}&\xrightarrow{+\dfrac{3}{8}}&\boxed{\phantom{0000}}&\xrightarrow{-\dfrac{1}{4}}&\boxed{\phantom{0000}}\\\boxed{\dfrac{7}{16}}&\xrightarrow{+\dfrac{3}{8}}&\boxed{\phantom{0000}}&\xrightarrow{-\dfrac{1}{4}}&\boxed{\phantom{0000}}\\\boxed{\dfrac{1}{6}}&\xrightarrow{+\dfrac{3}{8}}&\boxed{\phantom{0000}}&\xrightarrow{-\dfrac{1}{4}}&\boxed{\phantom{0000}}\end{array}$
$\begin{array}{ccc}\boxed{\dfrac{3}{5}}&\xrightarrow{-\dfrac{1}{6}}&\boxed{\phantom{0000}}&\xrightarrow{+\dfrac{3}{10}}&\boxed{\phantom{0000}}\\\boxed{\dfrac{7}{10}}&\xrightarrow{-\dfrac{1}{6}}&\boxed{\phantom{0000}}&\xrightarrow{+\dfrac{3}{10}}&\boxed{\phantom{0000}}\\\boxed{\dfrac{4}{15}}&\xrightarrow{-\dfrac{1}{6}}&\boxed{\phantom{0000}}&\xrightarrow{+\dfrac{3}{10}}&\boxed{\phantom{0000}}\end{array}$

1.左:1 $\boldsymbol{\frac{3}{4}}$ 右:$\boldsymbol{\frac{13}{30}}$ $\boldsymbol{\frac{11}{15}}$
$\boldsymbol{\frac{13}{16}}$ $\boldsymbol{\frac{9}{16}}$ $\boldsymbol{\frac{8}{15}}$ $\boldsymbol{\frac{5}{6}}$
$\boldsymbol{\frac{13}{24}}$ $\boldsymbol{\frac{7}{24}}$ $\boldsymbol{\frac{1}{10}}$ $\boldsymbol{\frac{2}{5}}$

2. 下面的计算对吗？把不对的改正过来。
(1) $\begin{align}\dfrac{1}{4}+\dfrac{5}{8}-\dfrac{5}{12}&=\dfrac{6}{24}+\dfrac{15}{24}-\dfrac{10}{24}\\&=\dfrac{21}{24}-\dfrac{10}{24}\\&=\dfrac{11}{24}\end{align}$ ( )
(2) $\begin{align}\dfrac{7}{8}-\dfrac{1}{2}-\dfrac{1}{3}&=\dfrac{7}{8}-(\dfrac{1}{2}-\dfrac{1}{3})\\&=\dfrac{7}{8}-\dfrac{1}{6}\\&=\dfrac{17}{24}\end{align}$ ( )

2.(1)√ (2)× $\boldsymbol{\frac{1}{24}}$

3. 计算。
$\dfrac{8}{9}+\dfrac{5}{6}-\dfrac{2}{3}$ $\dfrac{3}{4}-\dfrac{5}{8}+\dfrac{5}{6}$ $\dfrac{2}{5}+(\dfrac{5}{6}-\dfrac{2}{3})$ $\dfrac{2}{3}+(\dfrac{1}{4}+\dfrac{3}{8})$

3. $\boldsymbol{\frac{19}{18}}$ $\boldsymbol{\frac{23}{24}}$ $\boldsymbol{\frac{17}{30}}$ $\boldsymbol{\frac{31}{24}}$

4. 小东身高$\dfrac{9}{10}\mathrm{ m}$，比小玲矮$\dfrac{1}{8}\mathrm{ m}$。小刚比小玲矮$\dfrac{1}{20}\mathrm{ m}$，小刚身高是多少米？

4. $\boldsymbol{\frac{9}{10}+\frac{1}{8}-\frac{1}{20}=\frac{39}{40}}$(m)