4. 在“$○$”里填上“＞”、“＜”或“=”。
$\frac{2}{3}○$$0.66$
$0.5○$$5\%$
$0.09○$$\frac{9}{101}$
$\frac{19}{4}○$$4\frac{3}{4}$
$0.3○$$30\%$
$75\%○$$\frac{4}{5}$
$133.3\%○$$1\frac{1}{3}$
$130\%○$$1\frac{1}{2}$

$\frac{2}{3}＞0.66$
$0.5＞5\%$
$0.09＜\frac{9}{101}$
$\frac{19}{4}=4\frac{3}{4}$
$0.3=30\%$
$75\%＜\frac{4}{5}$
$133.3\%＜1\frac{1}{3}$
$130\%＜1\frac{1}{2}$

(1)直接写得数。
$6×\frac{5}{6}=$
$\frac{2}{5}×\frac{2}{5}=$
$\frac{1}{6}×\frac{3}{10}=$
$\frac{6}{5}×\frac{5}{7}×\frac{7}{6}=$
$44÷\frac{11}{10}=$
$\frac{6}{7}×\frac{5}{9}=$
$\frac{1}{9}÷\frac{2}{3}=$
$\frac{5}{18}÷\frac{3}{7}÷\frac{7}{3}=$

5
$\frac{4}{25}$
$\frac{1}{20}$
1
40
$\frac{10}{21}$
$\frac{1}{6}$
$\frac{5}{18}$

(2)求比值。
35:45
0.3:0.15
18:$\frac{2}{3}$
1:0.125
$\frac{3}{20}:\frac{4}{5}$
6:0.36
$\frac{0.8}{10}$
$\frac{72}{90}$

35:45 = 35÷45 = 7/9
0.3:0.15 = 0.3÷0.15 = 2
18:2/3 = 18÷(2/3) = 27
1:0.125 = 1÷0.125 = 8
3/20:4/5 = (3/20)÷(4/5) = 3/16
6:0.36 = 6÷0.36 = 50/3
0.8/10 = 0.8÷10 = 0.08
72/90 = 72÷90 = 4/5

(3)计算下列各题。
$\frac{1}{8}×14÷\frac{7}{8}$
$0.7×\frac{5}{16}÷\frac{21}{32}$
$2-\frac{3}{8}÷\frac{7}{16}-\frac{1}{7}$
$10×(\frac{8}{5}-\frac{1}{4}÷0.25)$

$\frac{1}{8}×14÷\frac{7}{8}$
$=\frac{1}{8}×14×\frac{8}{7}$
$=\frac{1}{8}×\frac{8}{7}×14$
$=\frac{1}{7}×14$
$=2$
$0.7×\frac{5}{16}÷\frac{21}{32}$
$=\frac{7}{10}×\frac{5}{16}×\frac{32}{21}$
$=\frac{7}{10}×(\frac{5}{16}×\frac{32}{21})$
$=\frac{7}{10}×\frac{10}{21}$
$=\frac{1}{3}$
$2 - \frac{3}{8}÷\frac{7}{16} - \frac{1}{7}$
$=2 - \frac{3}{8}×\frac{16}{7} - \frac{1}{7}$
$=2 - \frac{6}{7} - \frac{1}{7}$
$=2 - (\frac{6}{7} + \frac{1}{7})$
$=2 - 1$
$=1$
$10×(\frac{8}{5} - \frac{1}{4}÷0.25)$
$=10×(\frac{8}{5} - \frac{1}{4}÷\frac{1}{4})$
$=10×(\frac{8}{5} - 1)$
$=10×\frac{3}{5}$
$=6$

(4)解方程。
$\frac{3}{5}x= \frac{9}{10}$
$\frac{4}{5}+x= \frac{8}{9}$
$18-1.5x= 5.5$

$\frac{3}{5}x=\frac{9}{10}$
解：$x=\frac{9}{10}÷\frac{3}{5}$
$x=\frac{9}{10}×\frac{5}{3}$
$x=\frac{3}{2}$
$\frac{4}{5}+x=\frac{8}{9}$
解：$x=\frac{8}{9}-\frac{4}{5}$
$x=\frac{40}{45}-\frac{36}{45}$
$x=\frac{4}{45}$
$18 - 1.5x=5.5$
解：$1.5x=18 - 5.5$
$1.5x=12.5$
$x=12.5÷1.5$
$x=\frac{25}{3}$

(1)消毒酒精是由纯酒精和蒸馏水配制而成的,纯酒精与蒸馏水的比是3:1。用600毫升纯酒精配制消毒酒精,要加蒸馏水多少毫升？

设要加蒸馏水$x$毫升。
因为纯酒精与蒸馏水的比是$3:1$，所以$600:x = 3:1$
根据比例的性质，$3x = 600×1$
$3x = 600$
$x = 600÷3$
$x = 200$
答：要加蒸馏水200毫升。