1. $\frac{3}{5}$的分数单位是( ),$\frac{7}{9}$的分数单位是( ),所以计算$\frac{3}{5} + \frac{7}{9}$时不能直接( ),应先( ),再进行计算。
答案:
$\frac{1}{5}$ $\frac{1}{9}$ 相加 通分
2. $\frac{2}{5} + \frac{3}{7} = \frac{(\ \ \ \ \ \ )}{35} + \frac{(\ \ \ \ \ \ )}{35} = (\ \ \ \ \ \ )$
答案:
14 15 $\frac{29}{35}$
3. $\frac{3}{8} - \frac{2}{9} = (\ \ \ \ \ \ ) - (\ \ \ \ \ \ ) = (\ \ \ \ \ \ )$
答案:
$\frac{27}{72}$ $\frac{16}{72}$ $\frac{11}{72}$
二、看图计算我能行。
1.
$\frac{1}{4} + \frac{1}{8} = (\ \ ) + (\ \ ) = (\ \ )$
2.
1.
$\frac{1}{4} + \frac{1}{8} = (\ \ ) + (\ \ ) = (\ \ )$
2.
答案:
1. $\frac{2}{8}$ $\frac{1}{8}$ $\frac{3}{8}$ 2. $\frac{1}{3}$ $\frac{1}{6}$ $\frac{2}{6}$ $\frac{1}{6}$ $\frac{1}{2}$
三、数学门诊部。(对的打“√”,错的打“×”)
$\frac{4}{5} + \frac{2}{3} = \frac{6}{15}(\ \ \ \ \ \ )$
$\frac{5}{14} - \frac{2}{7} = \frac{3}{7}(\ \ \ \ \ \ )$
$\frac{8}{9} - \frac{1}{3} = \frac{7}{6}(\ \ \ \ \ \ )$
$\frac{7}{8} + \frac{1}{16} = \frac{15}{16}(\ \ \ \ \ \ )$
$\frac{4}{5} + \frac{2}{3} = \frac{6}{15}(\ \ \ \ \ \ )$
$\frac{5}{14} - \frac{2}{7} = \frac{3}{7}(\ \ \ \ \ \ )$
$\frac{8}{9} - \frac{1}{3} = \frac{7}{6}(\ \ \ \ \ \ )$
$\frac{7}{8} + \frac{1}{16} = \frac{15}{16}(\ \ \ \ \ \ )$
答案:
× × × √
四、分一分,填序号。
①$\frac{1}{3} + \frac{1}{4}$ ②$\frac{1}{5} + \frac{1}{7}$
③$\frac{5}{8} - \frac{1}{4}$ ④$\frac{7}{8} - \frac{1}{3}$
⑤$\frac{2}{5} + \frac{1}{6}$ ⑥$\frac{11}{12} - \frac{1}{4}$
⑦$\frac{3}{4} - \frac{1}{2}$ ⑧$\frac{5}{6} - \frac{1}{4}$
①$\frac{1}{3} + \frac{1}{4}$ ②$\frac{1}{5} + \frac{1}{7}$
③$\frac{5}{8} - \frac{1}{4}$ ④$\frac{7}{8} - \frac{1}{3}$
⑤$\frac{2}{5} + \frac{1}{6}$ ⑥$\frac{11}{12} - \frac{1}{4}$
⑦$\frac{3}{4} - \frac{1}{2}$ ⑧$\frac{5}{6} - \frac{1}{4}$
答案:
得数大于$\frac{1}{2}$:①④⑤⑥⑧ 得数小于$\frac{1}{2}$:②③⑦
五、开心算一算。
$\frac{5}{6} + \frac{1}{2} =$ $\frac{2}{3} + \frac{1}{4} =$
$\frac{4}{12} - \frac{3}{20} =$ $\frac{4}{15} - \frac{1}{4} =$
$\frac{5}{6} + \frac{1}{2} =$ $\frac{2}{3} + \frac{1}{4} =$
$\frac{4}{12} - \frac{3}{20} =$ $\frac{4}{15} - \frac{1}{4} =$
答案:
$\frac{4}{3}$ $\frac{11}{12}$ $\frac{11}{60}$ $\frac{1}{60}$
六、三级跳远。
答案:
1. $\frac{55}{56}$ $\frac{65}{56}$ 2. $\frac{2}{9}$ $\frac{1}{6}$
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