一、口算。
$\frac{7}{10}-\frac{2}{10}=$ $\frac{2}{5}+\frac{2}{5}=$ $\frac{19}{24}-\frac{13}{24}=$
$\frac{5}{8}+\frac{1}{8}=$ $\frac{12}{15}-\frac{8}{15}=$ $\frac{19}{36}+\frac{3}{36}=$
$\frac{8}{17}-\frac{2}{17}=$ $\frac{5}{13}+\frac{7}{13}=$ $\frac{20}{19}-\frac{7}{19}=$
$4÷0.04=$ $4.15-0.85=$ $7.5×4=$
$0.13×7=$ $64÷0.4=$ $0.76-0.6=$
$10-1.11=$ $0.36×2=$ $0.19+0.08=$
$14+1.4=$ $8.1÷0.3=$ $6×0.125=$
$0.09×8=$ $0.24+1.76=$ $4.8-2.08=$
$3.5+7.6=$ $1.16×0.7=$ $3.2÷0.08=$
$1.6÷80=$ $2.5-0.04=$ $3.8×0.3=$

$\frac{1}{2}$ $\frac{4}{5}$ $\frac{1}{4}$
$\frac{3}{4}$ $\frac{4}{15}$ $\frac{11}{18}$
$\frac{6}{17}$ $\frac{12}{13}$ $\frac{13}{19}$
$100$ $3.3$ $30$
$0.91$ $160$ $0.16$
$8.89$ $0.72$ $0.27$
$15.4$ $27$ $0.75$
$0.72$ $2$ $2.72$
$11.1$ $0.812$ $40$
$0.02$ $2.46$ $1.14$

二、先通分，再比较大小。
$\frac{4}{9}$和$\frac{5}{6}$ $\frac{3}{10}$和$\frac{7}{15}$ $\frac{19}{27}$和$\frac{5}{9}$

$\frac{4}{9}=\frac{8}{18}$ $\frac{5}{6}=\frac{15}{18}$ $\frac{4}{9}＜\frac{5}{6}$
$\frac{3}{10}=\frac{9}{30}$ $\frac{7}{15}=\frac{14}{30}$ $\frac{3}{10}＜\frac{7}{15}$
$\frac{19}{27}=\frac{19}{27}$ $\frac{5}{9}=\frac{15}{27}$ $\frac{19}{27}＞\frac{5}{9}$