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第7頁

信息發(fā)布者：

$\frac{1}{2}$

$\frac{9}{10}$

$\frac{4}{3}$

$\frac{12}{35}$

$0.09$

$1$

$\frac{3}{7}$

$\frac{1}{12}$

$\frac{1}{2}$

$\frac{3}{4}$

 $\begin{aligned}&\frac{2}{3}+\frac{4}{5}-\frac{3}{10}\\=&\frac{20}{30}+\frac{24}{30}-\frac{9}{30}\\=&\frac{20 + 24 - 9}{30}\\=&\frac{35}{30}\\=&\frac{7}{6}\end{aligned}$

 $\begin{aligned}&\frac{7}{13}-\frac{2}{5}+\frac{8}{13}-\frac{3}{5}\\=&(\frac{7}{13}+\frac{8}{13})-(\frac{2}{5}+\frac{3}{5})\\=&\frac{15}{13}-1\\=&\frac{2}{13}\end{aligned}$

 $\begin{aligned}&\frac{7}{9}-(\frac{1}{6}-\frac{2}{9})\\=&\frac{7}{9}-\frac{1}{6}+\frac{2}{9}\\=&(\frac{7}{9}+\frac{2}{9})-\frac{1}{6}\\=&1-\frac{1}{6}\\=&\frac{5}{6}\end{aligned}$

 $\begin{aligned}&1-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}\\=&1-(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32})\\=&1-(\frac{16}{32}+\frac{8}{32}+\frac{4}{32}+\frac{2}{32}+\frac{1}{32})\\=&1-\frac{31}{32}\\=&\frac{1}{32}\end{aligned}$

解:

?$ \begin {aligned}0.6x\div 2&=1.8\\0.6x&=1.8×2\\0.6x&=3.6\\x &=3.6\div 0.6\\x &=6\end {aligned}$?

解:

 $\begin{aligned}0.75x - 0.5x&=1\\0.25x&=1\\x&=1\div0.25\\x&=4\end{aligned}$

解:

 $\begin{aligned}6\times0.8 + 7x&=19.5\\4.8+7x&=19.5\\7x&=19.5 - 4.8\\7x&=14.7\\x&=14.7\div7\\x&=2.1\end{aligned}$

 $\begin{aligned}&9\times2 + 6+3.14\times6\div2\\=&18 + 6+9.42\\=&24+9.42\\=&33.42(\text{dm})\end{aligned}$

 $\begin{aligned}&10\div2 = 5(\text{cm})\\&3.14\times5^2-10\times5\div2\times2\\=&3.14\times25 - 50\\=&78.5 - 50\\=&28.5(\text{cm}^2)\end{aligned}$

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第7頁