一、口算。
拍照批改
$4.28 + 3.2 =$ $3.14×4 =$ $\dfrac{2}{5}÷\dfrac{2}{3} =$
$20×51 =$ $7.2 - 0.72 =$ $4.4 + 16 =$
$\dfrac{4}{5}÷\dfrac{8}{15} =$ $\dfrac{5}{8}×\dfrac{16}{15} =$ $900÷15 =$
$200×260\% =$ $\dfrac{3}{4}÷\dfrac{1}{8} =$ $\dfrac{2}{15} - \dfrac{1}{30} =$
$15÷40 =$ $\dfrac{5}{8} - \dfrac{3}{10} =$ $\dfrac{7}{25}×\dfrac{5}{7} =$
$\dfrac{2}{5}×\dfrac{5}{8} =$ $\dfrac{1}{6} + \dfrac{4}{11} =$ $\dfrac{5}{4}÷\dfrac{4}{5} =$
$\dfrac{3}{8} + \dfrac{1}{3} =$ $4÷\dfrac{1}{4} =$ $\dfrac{2}{15}×\dfrac{5}{12} =$

一、7.48 12.56 $\dfrac{3}{5}$ 1020 6.48 20.4 $\dfrac{3}{2}$ $\dfrac{2}{3}$ 60 520 6 $\dfrac{1}{10}$ $\dfrac{3}{8}$ $\dfrac{13}{40}$ $\dfrac{1}{5}$ $\dfrac{1}{4}$ $\dfrac{35}{66}$ $\dfrac{25}{16}$ $\dfrac{17}{24}$ 16 $\dfrac{1}{18}$

二、解比例。
$\dfrac{2.5}{3} = \dfrac{10}{x}$ $1.2:5 = 24:x$ $\dfrac{1}{3}:\dfrac{2}{5} = x:\dfrac{3}{4}$
$x:12 = 0.16:16$ $4.5:\dfrac{3}{4} = x:\dfrac{4}{3}$ $0.6:x = \dfrac{1}{24}:\dfrac{1}{8}$

二、$x = 12$ $x = 100$ $x = \dfrac{5}{8}$ $x = 0.12$ $x = 8$ $x = 1.8$

$\dfrac{2.5}{3} = \dfrac{10}{x}$
解：$2.5x = 3×10$
$2.5x = 30$
$x = 30÷2.5$
$x = 12$
$1.2:5 = 24:x$
解：$1.2x = 5×24$
$1.2x = 120$
$x = 120÷1.2$
$x = 100$
$\dfrac{1}{3}:\dfrac{2}{5} = x:\dfrac{3}{4}$
解：$\dfrac{2}{5}x = \dfrac{1}{3}×\dfrac{3}{4}$
$\dfrac{2}{5}x = \dfrac{1}{4}$
$x = \dfrac{1}{4}÷\dfrac{2}{5}$
$x = \dfrac{1}{4}×\dfrac{5}{2}$
$x = \dfrac{5}{8}$
$x:12 = 0.16:16$
解：$16x = 12×0.16$
$16x = 1.92$
$x = 1.92÷16$
$x = 0.12$
$4.5:\dfrac{3}{4} = x:\dfrac{4}{3}$
解：$\dfrac{3}{4}x = 4.5×\dfrac{4}{3}$
$\dfrac{3}{4}x = 6$
$x = 6÷\dfrac{3}{4}$
$x = 6×\dfrac{4}{3}$
$x = 8$
$0.6:x = \dfrac{1}{24}:\dfrac{1}{8}$
解：$\dfrac{1}{24}x = 0.6×\dfrac{1}{8}$
$\dfrac{1}{24}x = 0.075$
$x = 0.075×24$
$x = 1.8$