一、口算。
$3.86 + 0.5 =$ $3.9 ÷ 10\% =$ $400 × 0.9 =$
$0.78 ÷ 13 =$ $2.65 × 0.3 =$ $305 + 405 =$
$25 × 0.04 =$ $9 ÷ 3\% =$ $20 × 0.16 =$
$0.72 ÷ 0.12 =$ $3.14 × 0.4 =$ $3.15 - 0.09 =$
$1 - 44\% =$ $51 ÷ 34 =$ $\dfrac{4}{5} - \dfrac{4}{15} =$
$\dfrac{5}{8} × \dfrac{2}{5} =$ $\dfrac{3}{4} - \dfrac{1}{6} =$ $\dfrac{9}{14} × \dfrac{7}{45} =$
$\dfrac{1}{4} + \dfrac{3}{4} =$ $\dfrac{2}{5} ÷ \dfrac{5}{12} =$ $\dfrac{5}{6} + \dfrac{1}{3} =$
$\dfrac{13}{24} ÷ \dfrac{13}{18} =$ $\dfrac{2}{3} × \dfrac{9}{16} =$ $\dfrac{11}{20} ÷ \dfrac{11}{15} =$
$3 + 20\% =$ $\dfrac{3}{2} - \dfrac{5}{4} =$ $\dfrac{3}{4} ÷ \dfrac{5}{6} =$
$\dfrac{5}{12} + \dfrac{1}{8} =$ $\dfrac{19}{20} × \dfrac{10}{57} =$ $\dfrac{4}{7} - \dfrac{1}{3} =$

一、4.36 39 360
0.06 0.795 710
1 300 3.2
6 1.256 3.06
0.56 1.5 $\frac{8}{15}$
$\frac{1}{4}$ $\frac{7}{12}$ $\frac{1}{10}$
1 $\frac{24}{25}$ $\frac{7}{6}$
$\frac{3}{4}$ $\frac{3}{8}$ $\frac{3}{4}$
3.2 $\frac{1}{4}$ $\frac{9}{10}$
$\frac{13}{24}$ $\frac{1}{6}$ $\frac{5}{21}$

二、计算下面各题。
$6.78 - 5.2 ÷ 0.8 × 0.6$ $\dfrac{1}{8} + \dfrac{1}{2} ÷ 4 + \dfrac{3}{4}$ $208 × 33 - 2050 ÷ 50$
$(23.1 + 5.7) ÷ (1.5 × 6)$ $\dfrac{7}{15} ÷ [\dfrac{1}{5} × (\dfrac{1}{3} - \dfrac{1}{4})]$

二、2.88 1 6823
3.2 28