一、口算。
$1.8÷5=$ $1.6+0.44=$ $\frac {6}{5}-\frac {5}{6}=$
$62.5\% ÷\frac {4}{5}=$ $18÷\frac {4}{9}=$ $3.6×10\% =$
$\frac {3}{4}+50\% =$ $\frac {34}{39}÷\frac {17}{13}=$ $1.85×0.4=$
$\frac {6}{5}×\frac {3}{8}=$ $0.76+3.34=$ $4.5÷1.8=$
$2.5-0.7=$ $\frac {6}{7}×\frac {7}{78}=$ $\frac {5}{6}+\frac {15}{16}=$
$160÷200=$ $\frac {3}{14}+\frac {6}{7}=$ $\frac {5}{8}-\frac {1}{4}=$
$20\% ×\frac {3}{4}=$ $35\% ×20\% =$ $\frac {3}{22}÷\frac {9}{11}=$
$0.85÷15=$ $7.6+\frac {8}{5}=$ $1.9÷38\% =$

一、0.36 2.04 $\dfrac{11}{30}$ $\dfrac{25}{32}$ $\dfrac{81}{2}$ 0.36 $\dfrac{5}{4}$ $\dfrac{2}{3}$ 0.74 $\dfrac{9}{20}$ 4.1 2.5 1.8 $\dfrac{1}{13}$ $\dfrac{85}{48}$ 0.8 $\dfrac{15}{14}$ $\dfrac{3}{8}$ $\dfrac{3}{20}$ 0.07 $\dfrac{1}{6}$ $\dfrac{17}{300}$ 9.2 5

二、求未知角的度数。

二、$∠ 1 = 180^{\circ} - 125^{\circ} = 55^{\circ}$ $∠ 2 = 360^{\circ} - 90^{\circ} - 115^{\circ} - 55^{\circ} = 100^{\circ}$ $∠ 3 = 180^{\circ} - 35^{\circ} × 2 = 110^{\circ}$