1 计算下面各题。
$\frac{27}{50} × 2$
$\frac{11}{28} × \frac{8}{33}$
$\frac{20}{39} × 7.8$
$\frac{7}{18} × 0.36$
$\frac{9}{16} × 0.3$
$\frac{5}{54} × 6.75$
答案：$\frac{27}{50} × 2 = \frac{27}{25}$
$\frac{11}{28} × \frac{8}{33} = \frac{2}{21}$
$\frac{20}{39} × 7.8 =4$
$\frac{7}{18} × 0.36 =0.14$
$\frac{9}{16} × 0.3 = \frac{27}{160}$
$\frac{5}{54} × 6.75 = \frac{5}{8}$
② 鸵鸟是目前世界上最大的鸟。一只鸵鸟的身高是2.5 m，一只成年帝企鹅的身高是鸵鸟的$\frac{12}{25}$。这只成年帝企鹅的身高是多少米？
答案：$2.5 × \frac{12}{25} =1.2$（m）
答：这只成年帝企鹅的身高是1.2 m。
3 计算下面各题。
$\frac{1}{3} × \frac{3}{5} + 1$
$\frac{5}{7} - \frac{5}{9} × \frac{5}{7}$
$1 - \frac{15}{28} × \frac{21}{25}$
$\frac{1}{2} + \frac{5}{4} × \frac{4}{5}$
$\frac{1}{6} × (5 - \frac{2}{3})$
$\frac{7}{8} × 7 + \frac{3}{8}$
答案：$\frac{1}{3} × \frac{3}{5} + 1= \frac{6}{5}$
$\frac{5}{7} - \frac{5}{9} × \frac{5}{7} = \frac{20}{63}$
$1 - \frac{15}{28} × \frac{21}{25} = \frac{11}{20}$
$\frac{1}{2} + \frac{5}{4} × \frac{4}{5} = \frac{3}{2}$
$\frac{1}{6} × (5 - \frac{2}{3}) = \frac{13}{18}$
$\frac{7}{8} × 7 + \frac{3}{8} = \frac{13}{2}$
4 下面各题算得对吗？把不对的改正过来。
$5 - 3×\frac{7}{9} = 2×\frac{7}{9} = \frac{14}{9}$
$( \frac{1}{6} + \frac{3}{4} )×6 = 1 + \frac{3}{4} = \frac{7}{4}$
答案：不对。改正：$5-3×\frac{7}{9}=5-\frac{7}{3}=\frac{8}{3}$
不对。改正：$(\frac{1}{6}+\frac{3}{4})×6=1+\frac{9}{2}=\frac{11}{2}$
5 用运算律进行简便计算。
$\frac{2}{9} - \frac{7}{16} × \frac{2}{9}$
$\frac{2}{27} × 4 × \frac{3}{4}$
$\frac{5}{7} × 16 × \frac{42}{25}$
$\frac{1}{2} × \frac{1}{15} + \frac{1}{3} × \frac{1}{2}$
$\frac{4}{5} × \frac{7}{9} × \frac{15}{8}$
$\frac{5}{6} × \frac{5}{9} + \frac{5}{9} × \frac{1}{6}$
答案：$\frac{2}{9} - \frac{7}{16} × \frac{2}{9} = \frac{1}{8}$
$\frac{2}{27} × 4 × \frac{3}{4} = \frac{2}{9}$
$\frac{5}{7} × 16 × \frac{42}{25} = \frac{96}{5}$
$\frac{1}{2} × \frac{1}{15} + \frac{1}{3} × \frac{1}{2} = \frac{1}{5}$
$\frac{4}{5} × \frac{7}{9} × \frac{15}{8} = \frac{7}{6}$
$\frac{5}{6} × \frac{5}{9} + \frac{5}{9} × \frac{1}{6} = \frac{5}{9}$
6 计算下面各题，能用简便算法的就用简便算法。
$\frac{11}{24} × 16$
$\frac{1}{4} × \frac{2}{7}$
$\frac{7}{12} × 6 + \frac{17}{12} × 6$
$\frac{3}{5} × \frac{55}{6}$
$\frac{4}{9} × 5 × 18$
$( 14 + \frac{7}{2} ) × \frac{1}{14}$
答案：$\frac{11}{24} × 16 = \frac{22}{3}$
$\frac{1}{4} × \frac{2}{7} = \frac{1}{14}$
$\frac{7}{12} × 6 + \frac{17}{12} × 6 =12$
$\frac{3}{5} × \frac{55}{6} = \frac{11}{2}$
$\frac{4}{9} × 5 × 18 =40$
$( 14 + \frac{7}{2} ) × \frac{1}{14} = \frac{5}{4}$
