一、直接写出得数。
$\frac{3}{4}+\frac{1}{5}=$ $\frac{2}{5}+\frac{1}{7}=$ $\frac{6}{7}-\frac{5}{21}=$ $\frac{2}{5}+\frac{1}{2}=$
$\frac{8}{9}-\frac{2}{3}=$ $\frac{3}{8}+\frac{8}{5}=$ $\frac{3}{4}-\frac{2}{5}=$ $\frac{1}{4}-\frac{1}{7}=$
$\frac{3}{7}+\frac{1}{2}=$ $\frac{5}{6}-\frac{2}{5}=$ $\frac{9}{32}+\frac{3}{8}=$ $\frac{3}{7}+\frac{3}{14}=$
$\frac{7}{12}-\frac{1}{3}=$ $1+\frac{5}{13}=$ $\frac{3}{5}-\frac{2}{7}=$ $\frac{2}{3}-\frac{1}{5}=$
$\frac{7}{10}+\frac{5}{6}=$ $\frac{7}{16}-\frac{1}{4}=$ $\frac{3}{8}+\frac{1}{12}=$ $\frac{1}{6}+\frac{1}{4}=$
$\frac{3}{4}+\frac{1}{5}=$ $\frac{2}{5}+\frac{1}{7}=$ $\frac{6}{7}-\frac{5}{21}=$ $\frac{2}{5}+\frac{1}{2}=$
$\frac{8}{9}-\frac{2}{3}=$ $\frac{3}{8}+\frac{8}{5}=$ $\frac{3}{4}-\frac{2}{5}=$ $\frac{1}{4}-\frac{1}{7}=$
$\frac{3}{7}+\frac{1}{2}=$ $\frac{5}{6}-\frac{2}{5}=$ $\frac{9}{32}+\frac{3}{8}=$ $\frac{3}{7}+\frac{3}{14}=$
$\frac{7}{12}-\frac{1}{3}=$ $1+\frac{5}{13}=$ $\frac{3}{5}-\frac{2}{7}=$ $\frac{2}{3}-\frac{1}{5}=$
$\frac{7}{10}+\frac{5}{6}=$ $\frac{7}{16}-\frac{1}{4}=$ $\frac{3}{8}+\frac{1}{12}=$ $\frac{1}{6}+\frac{1}{4}=$
答案:
$\frac{19}{20}$ $\frac{19}{35}$ $\frac{13}{21}$ $\frac{9}{10}$
$\frac{2}{9}$ $\frac{79}{40}$ $\frac{7}{20}$ $\frac{3}{28}$
$\frac{13}{14}$ $\frac{13}{30}$ $\frac{21}{32}$ $\frac{9}{14}$
$\frac{1}{4}$ $\frac{18}{13}$ $\frac{11}{35}$ $\frac{7}{15}$
$\frac{23}{15}$ $\frac{3}{16}$ $\frac{11}{24}$ $\frac{5}{12}$
二、计算下面各题,你发现了什么规律?
$\frac{1}{2}+\frac{1}{3}=$ $\frac{1}{5}+\frac{1}{6}=$ $\frac{1}{6}+\frac{1}{7}=$
$\frac{1}{2}-\frac{1}{3}=$ $\frac{1}{5}-\frac{1}{6}=$ $\frac{1}{6}-\frac{1}{7}=$
我发现:$m、n$均是非$0$自然数,且$m < n$,则$\frac{1}{m}+\frac{1}{n}=$______,$\frac{1}{m}-\frac{1}{n}=$______。
$\frac{1}{2}+\frac{1}{3}=$ $\frac{1}{5}+\frac{1}{6}=$ $\frac{1}{6}+\frac{1}{7}=$
$\frac{1}{2}-\frac{1}{3}=$ $\frac{1}{5}-\frac{1}{6}=$ $\frac{1}{6}-\frac{1}{7}=$
我发现:$m、n$均是非$0$自然数,且$m < n$,则$\frac{1}{m}+\frac{1}{n}=$______,$\frac{1}{m}-\frac{1}{n}=$______。
答案:
$\frac{5}{6}$ $\frac{11}{30}$ $\frac{13}{42}$
$\frac{1}{6}$ $\frac{1}{30}$ $\frac{1}{42}$
$\frac{m + n}{mn}$ $\frac{n - m}{mn}$
三、在$\bigcirc$里填上“$>$”“$<$”或“$=$”。
$\frac{2}{15}+\frac{7}{15}\bigcirc\frac{3}{5}$ $\frac{7}{8}-\frac{1}{3}\bigcirc\frac{1}{2}$ $1-\frac{13}{20}\bigcirc\frac{3}{10}+\frac{1}{4}$
$\frac{9}{10}-\frac{2}{5}\bigcirc\frac{2}{3}$ $\frac{1}{5}-\frac{1}{6}\bigcirc\frac{1}{30}$ $\frac{1}{2}+\frac{11}{24}\bigcirc1$
$\frac{2}{15}+\frac{7}{15}\bigcirc\frac{3}{5}$ $\frac{7}{8}-\frac{1}{3}\bigcirc\frac{1}{2}$ $1-\frac{13}{20}\bigcirc\frac{3}{10}+\frac{1}{4}$
$\frac{9}{10}-\frac{2}{5}\bigcirc\frac{2}{3}$ $\frac{1}{5}-\frac{1}{6}\bigcirc\frac{1}{30}$ $\frac{1}{2}+\frac{11}{24}\bigcirc1$
答案:
= > < < = <
四、计算下面各题,能简算的要简算。
$\frac{1}{12}+\frac{2}{11}+\frac{11}{12}$ $\frac{10}{9}+\frac{1}{3}+\frac{1}{3}+\frac{8}{9}$ $\frac{9}{10}-\frac{1}{6}-\frac{4}{15}$
$\frac{1}{12}+\frac{2}{11}+\frac{11}{12}$ $\frac{10}{9}+\frac{1}{3}+\frac{1}{3}+\frac{8}{9}$ $\frac{9}{10}-\frac{1}{6}-\frac{4}{15}$
答案:
$1\frac{2}{11}$ $2\frac{2}{3}$ $\frac{7}{15}$
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