1. 直接写出得数。(20☆)
$\frac{4}{5}×\frac{3}{8}=$
$\frac{5}{6}×\frac{4}{7}=$
$\frac{2}{9}×\frac{3}{4}=$
$\frac{3}{8}×\frac{4}{9}=$
$\frac{7}{8}×\frac{4}{7}=$
$\frac{5}{9}×\frac{3}{10}=$
$\frac{3}{7}×\frac{7}{9}=$
$\frac{5}{8}×3.2=$
$\frac{7}{9}×0.27=$
$\frac{4}{11}×3.3=$
$3.5×\frac{3}{7}=$
$1.5×\frac{4}{5}=$
$\frac{5}{11}×\frac{22}{25}=$
$\frac{9}{16}×\frac{8}{27}=$
$\frac{4}{15}×\frac{5}{12}=$
$\frac{13}{12}×\frac{15}{26}=$
$\frac{3}{7}×\frac{14}{15}×\frac{5}{6}=$
$\frac{5}{12}×\frac{6}{7}×\frac{2}{5}=$
$20×\frac{3}{5}×\frac{1}{6}=$
$1.8×\frac{2}{3}×\frac{1}{6}=$

$\frac{3}{10}$
$\frac{10}{21}$
$\frac{1}{6}$
$\frac{1}{6}$
$\frac{1}{2}$
$\frac{1}{6}$
$\frac{1}{3}$
$2$
$\frac{21}{100}$
$\frac{6}{5}$
$\frac{3}{2}$
$\frac{6}{5}$
$\frac{2}{5}$
$\frac{1}{6}$
$\frac{1}{9}$
$\frac{5}{8}$
$\frac{1}{3}$
$\frac{1}{7}$
$2$
$\frac{1}{5}$

2. 看图列式计算。(4☆)
(1)
(2)

(1)$56×\frac{5}{7}=40$(本)
$40×\frac{3}{5}=24$(本)
(2)$36×\frac{2}{3}=24$(个)
$24×\frac{3}{4}=18$(个)

3. 计算下面各题,能简算的要简算。(18☆)
$\frac{3}{4}×\frac{2}{5}+\frac{3}{4}×\frac{3}{5}$
$\frac{4}{5}×\frac{3}{7}+\frac{4}{5}×\frac{4}{7}$
$\frac{2}{9}×\frac{3}{4}+\frac{2}{9}×\frac{1}{4}$
$1.2×(\frac{1}{5}+\frac{1}{4})$
$\frac{5}{6}×(\frac{3}{4}-\frac{1}{2})$
$(\frac{4}{7}+\frac{2}{3})×2.1$

$\frac{3}{4}$
$\frac{4}{5}$
$\frac{2}{9}$
$\frac{27}{50}$
$\frac{5}{24}$
$\frac{13}{5}$

4. 学校图书馆新购进800本图书，其中科普类书籍占$\frac{3}{5}$，而科普类书籍中天文类书籍又占$\frac{1}{4}$。天文类书籍有多少本？（8☆）

$800×\frac{3}{5}×\frac{1}{4}=120$(本)
答:天文类书籍有120本。