1. 直接写出得数。(12分)
$3 ÷ 15 \%$ $\frac {4}{7} × 2. 8 =$ $\frac {3}{4} + \frac {2}{5} =$ $\frac {5}{6} × \frac {4}{1 5} =$
$1 2 ÷ \frac {3}{4} =$ $1 - 25 \% =$ $\frac {1}{6} + \frac {1}{9} =$ $\frac {5}{8} × \frac {1}{4} =$
$0. 1 × 9 9 + 0. 1 =$ $\frac {1}{3} - \frac {1}{6} + \frac {1}{3} + \frac {1}{6} =$
$3 ÷ \frac {3}{7} - \frac {3}{7} ÷ 3 =$ $0. 2 5 × 3 9 + 0. 2 5 × 1 =$

1. 20 1.6 $\frac{23}{20}$(或$1\frac{3}{20}$) $\frac{2}{9}$ 16 0.75 $\frac{5}{18}$ $\frac{5}{32}$ 10 $\frac{2}{3}$ $\frac{48}{7}$(或$6\frac{6}{7}$) 10

2. 解比例。(12分)
$3 0: 7 = x: 3 5$ $\frac {x}{0 . 0 5} = \frac {4}{0 . 2}$ $6. 5: x = 3. 2 5: 4$
$1 2: 1 8 = 3 0: x$ $8: 2 1 = \frac {0 . 4}{x}$ $\frac {3}{8}: \frac {4}{1 1} = x: \frac {8}{3 3}$

2. $x=150$ $x=1$ $x=8$ $x=45$ $x=1.05$ $x=\frac{1}{4}$

3. 如图是一个大三角形按一定的比缩小成一个小三角形，列出比例式，并求出未知数 x。(单位：厘米)(4分)

3. $40:x=100:60$(列式不唯一) $x=24$