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$\frac {9}{5}×\frac {8}{9}×\frac {5}{8}=1(千米)$
$答:鸵鸟每分钟1千米。$
$\frac {7}{9}×\frac {3}{7}=\frac {1}{3}(米)$
$答:还剩\frac {1}{3}米。$
$\frac{7}{9} - \frac{3}{7} = \frac{22}{63}$(米)。
答:还剩$\frac{22}{63}$米。
3
4
4×5
4
5
5×6
5
6
$=1-\frac {1}{2}+\frac {1}{2}-\frac {1}{3}+\frac {1}{3}-\frac {1}{4}+\frac {1}{4}-\frac {1}{5}+\frac {1}{5}-\frac {1}{6}$
$=1-\frac {1}{6}$
$=\frac {5}{6}$