第89页

信息发布者:

$解:x=\frac{28}{15}×\frac{5}{7}$
       $x=\frac{4}{3}$

$解:1.3x=2.6$
             $x=2$
60
5

$=\frac{2}{7}×\frac{4}{9}+\frac{2}{7}×\frac{5}{9}\ $
$=\frac{2}{7}×(\frac{4}{9}+\frac {5}{9})$
$=\frac{2}{7}×1$
$=\frac {2}{7}$

$=42×\frac{14}{99}+31×\frac{14}{99}+26×\frac{14}{99}\ $
$=(42+31+26)×\frac{14}{99}\ $
$=99×\frac{14}{99}\ $
$=14$
因为$6*a=\frac{7}{4}\times6-\frac{5}{6}a=\frac{9}{2},$
$\frac{21}{2}-\frac{5}{6}a=\frac{9}{2},$$\frac{5}{6}a=\frac{21}{2}-\frac{9}{2}=6,$
$a = 6\div\frac{5}{6}=\frac{36}{5}。$
$\frac{5}{8}$

$实际质量:应称质量=900;1000=9:10\ $
$100×\frac{9}{10}=90(克)\ $
$100-90=10(克)\ $
$答:思萌还亏了10克。$

$(\frac{1}{2}+\frac{1}{3}+\frac{1}{5}+\frac{1}{7}+\frac{1}{11}+\frac{1}{13})×385\ $
$=\frac{1}{2}×385+\frac{1}{3}×385+\frac{1}{5}×385+\frac{1}{7}×385+\frac{1}{11}×385$
$+\frac{1}{13}×385\ $
$=192\frac{1}{2}+128\frac{1}{3}+77+55+35+29\frac{8}{13}\ $
$=(192+128+77+55+35+29)+ (\frac{1}{2}+\frac{1}{3}+\frac{8}{13})\ $
$=517+\frac{35}{78}\ $
$整数部分是517。$