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一、口算。
$\dfrac{7}{9}+\dfrac{2}{9}=$
$\dfrac{1}{5}+\dfrac{3}{5}=$
$\dfrac{4}{6}-\dfrac{3}{6}=$
$\dfrac{5}{13}+\dfrac{4}{13}=$
$\dfrac{5}{8}-\dfrac{3}{8}=$
$\dfrac{18}{10}-\dfrac{5}{10}=$
$\dfrac{7}{25}+\dfrac{17}{25}=$
$\dfrac{14}{15}-\dfrac{9}{15}=$
$\dfrac{7}{9}+\dfrac{2}{9}=$
1
$\dfrac{9}{20}+\dfrac{10}{20}=$$\dfrac{19}{20}$
$\dfrac{6}{13}-\dfrac{1}{13}=$$\dfrac{5}{13}$
$\dfrac{1}{5}+\dfrac{3}{5}=$
$\dfrac{4}{5}$
$\dfrac{13}{24}+\dfrac{6}{24}=$$\dfrac{19}{24}$
$\dfrac{8}{10}-\dfrac{5}{10}=$$\dfrac{3}{10}$
$\dfrac{4}{6}-\dfrac{3}{6}=$
$\dfrac{1}{6}$
$\dfrac{14}{5}-\dfrac{2}{5}=$$\dfrac{12}{5}$
$\dfrac{12}{7}+\dfrac{5}{7}=$$\dfrac{17}{7}$
$\dfrac{5}{13}+\dfrac{4}{13}=$
$\dfrac{9}{13}$
$\dfrac{10}{8}-\dfrac{2}{8}=$1
$\dfrac{7}{42}+\dfrac{34}{42}=$$\dfrac{41}{42}$
$\dfrac{5}{8}-\dfrac{3}{8}=$
$\dfrac{1}{4}$
$\dfrac{2}{11}+\dfrac{8}{11}=$$\dfrac{10}{11}$
$\dfrac{15}{16}-\dfrac{3}{16}=$$\dfrac{3}{4}$
$\dfrac{18}{10}-\dfrac{5}{10}=$
$\dfrac{13}{10}$
$\dfrac{3}{4}+\dfrac{5}{4}=$2
$\dfrac{8}{6}+\dfrac{4}{6}=$2
$\dfrac{7}{25}+\dfrac{17}{25}=$
$\dfrac{24}{25}$
$\dfrac{11}{12}-\dfrac{5}{12}=$$\dfrac{1}{2}$
$\dfrac{24}{25}-\dfrac{8}{25}=$$\dfrac{16}{25}$
$\dfrac{14}{15}-\dfrac{9}{15}=$
$\dfrac{1}{3}$
$\dfrac{25}{33}-\dfrac{3}{33}=$$\dfrac{2}{3}$
$\dfrac{4}{19}+\dfrac{6}{19}=$$\dfrac{10}{19}$
答案
一、1
$ \frac { 19 } { 20 } \frac { 5 } { 13 } $
$ \frac { 4 } { 5 } \frac { 19 } { 24 } \frac { 3 } { 10 } $
$ \frac { 1 } { 6 } \frac { 12 } { 5 } \frac { 17 } { 7 } $
$ \frac { 9 } { 13 } 1 \frac { 41 } { 42 } $
$ \frac { 1 } { 4 } \frac { 10 } { 11 } \frac { 3 } { 4 } $
$ \frac { 13 } { 10 } 2 2 \frac { 24 } { 25 } \frac { 1 } { 2 } \frac { 16 } { 25 } \frac { 1 } { 3 } \frac { 2 } { 3 } \frac { 10 } { 19 } $
$ \frac { 19 } { 20 } \frac { 5 } { 13 } $
$ \frac { 4 } { 5 } \frac { 19 } { 24 } \frac { 3 } { 10 } $
$ \frac { 1 } { 6 } \frac { 12 } { 5 } \frac { 17 } { 7 } $
$ \frac { 9 } { 13 } 1 \frac { 41 } { 42 } $
$ \frac { 1 } { 4 } \frac { 10 } { 11 } \frac { 3 } { 4 } $
$ \frac { 13 } { 10 } 2 2 \frac { 24 } { 25 } \frac { 1 } { 2 } \frac { 16 } { 25 } \frac { 1 } { 3 } \frac { 2 } { 3 } \frac { 10 } { 19 } $
二、先通分，再比较大小。
$\dfrac{7}{10}$和$\dfrac{8}{15}$ $\dfrac{6}{7}$和$\dfrac{19}{21}$ $\dfrac{15}{33}$和$\dfrac{9}{22}$
$\dfrac{3}{7}$和$\dfrac{4}{11}$ $\dfrac{2}{39}$和$\dfrac{5}{78}$ $\dfrac{7}{40}$和$\dfrac{5}{32}$
$\dfrac{7}{10}$和$\dfrac{8}{15}$ $\dfrac{6}{7}$和$\dfrac{19}{21}$ $\dfrac{15}{33}$和$\dfrac{9}{22}$
$\dfrac{3}{7}$和$\dfrac{4}{11}$ $\dfrac{2}{39}$和$\dfrac{5}{78}$ $\dfrac{7}{40}$和$\dfrac{5}{32}$
答案
二、$\frac{7}{10}=\frac{21}{30}$，$\frac{8}{15}=\frac{16}{30}$，因为$\frac{21}{30}＞\frac{16}{30}$，所以$\frac{7}{10}＞\frac{8}{15}$；
$\frac{6}{7}=\frac{18}{21}$，$\frac{19}{21}=\frac{19}{21}$，因为$\frac{18}{21}＜\frac{19}{21}$，所以$\frac{6}{7}＜\frac{19}{21}$；
$\frac{15}{33}=\frac{30}{66}$，$\frac{9}{22}=\frac{27}{66}$，因为$\frac{30}{66}＞\frac{27}{66}$，所以$\frac{15}{33}＞\frac{9}{22}$；
$\frac{3}{7}=\frac{33}{77}$，$\frac{4}{11}=\frac{28}{77}$，因为$\frac{33}{77}＞\frac{28}{77}$，所以$\frac{3}{7}＞\frac{4}{11}$；
$\frac{2}{39}=\frac{4}{78}$，$\frac{5}{78}=\frac{5}{78}$，因为$\frac{4}{78}＜\frac{5}{78}$，所以$\frac{2}{39}＜\frac{5}{78}$；
$\frac{7}{40}=\frac{28}{160}$，$\frac{5}{32}=\frac{25}{160}$，因为$\frac{28}{160}＞\frac{25}{160}$，所以$\frac{7}{40}＞\frac{5}{32}$。
$\frac{6}{7}=\frac{18}{21}$，$\frac{19}{21}=\frac{19}{21}$，因为$\frac{18}{21}＜\frac{19}{21}$，所以$\frac{6}{7}＜\frac{19}{21}$；
$\frac{15}{33}=\frac{30}{66}$，$\frac{9}{22}=\frac{27}{66}$，因为$\frac{30}{66}＞\frac{27}{66}$，所以$\frac{15}{33}＞\frac{9}{22}$；
$\frac{3}{7}=\frac{33}{77}$，$\frac{4}{11}=\frac{28}{77}$，因为$\frac{33}{77}＞\frac{28}{77}$，所以$\frac{3}{7}＞\frac{4}{11}$；
$\frac{2}{39}=\frac{4}{78}$，$\frac{5}{78}=\frac{5}{78}$，因为$\frac{4}{78}＜\frac{5}{78}$，所以$\frac{2}{39}＜\frac{5}{78}$；
$\frac{7}{40}=\frac{28}{160}$，$\frac{5}{32}=\frac{25}{160}$，因为$\frac{28}{160}＞\frac{25}{160}$，所以$\frac{7}{40}＞\frac{5}{32}$。
