一、口算。
$\frac{7}{12} + \frac{5}{12}=$ $20×3.14=$ $6.28÷3.14=$
$\frac{3}{8} - \frac{1}{12}=$ $10^{2}×3.14=$ $9.42÷3.14=$
$\frac{2}{3} + \frac{2}{7}=$ $40×3.14=$ $282.6÷3.14=$
$\frac{11}{12} - \frac{3}{5}=$ $0.1^{2}×3.14=$ $25.12÷3.14=$
$\frac{3}{2} + \frac{1}{3}=$ $500×3.14=$ $1256÷3.14=$
$\frac{9}{10} - \frac{3}{4}=$ $0.06×3.14=$ $21.98÷3.14=$
$\frac{8}{9} + \frac{1}{3}=$ $0.16×3.14=$ $18.84÷3.14=$
$\frac{7}{9} - \frac{2}{3}=$ $3^{2}×3.14=$ $31.4÷3.14=$
$\frac{7}{18} + \frac{1}{4}=$ $1000×3.14=$ $157÷3.14=$
$\frac{17}{18} - \frac{5}{6}=$ $1.8×3.14=$ $2.826÷3.14=$

1 62.8 2
$\frac{7}{24}$ 314 3
$\frac{20}{21}$ 125.6 90
$\frac{19}{60}$ 0.0314 8
$\frac{11}{6}$ 1570 400
$\frac{3}{20}$ 0.1884 7
$\frac{11}{9}$ 0.5024 6
$\frac{1}{9}$ 28.26 10
$\frac{23}{36}$ 3140 50
$\frac{1}{9}$ 5.652 0.9

二、计算下面各题，怎样简便就怎样计算。
$\frac{17}{12} - (\frac{2}{3} - \frac{1}{12})$ $\frac{7}{12} - \frac{3}{16} + \frac{1}{4}$ $\frac{13}{16} - (\frac{3}{7} - \frac{3}{16}) - \frac{4}{7}$

$\frac{5}{6}$ $\frac{31}{48}$ 0