第115页

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$\frac{2}{5}÷\frac{1}{5}×\frac{3}{4}=\frac{3}{2}$(千米)
$30 ÷ \dfrac{1}{5} × \dfrac{3}{5} = 90(\mathrm{千瓦}·\mathrm{时})$
$15 ÷ \dfrac{3}{5} × \dfrac{1}{5} = 5(\mathrm{千克})$
$1÷(\frac{1}{8}+\frac{1}{10})=\frac{40}{9}$(小时)
(1)水田:$0.78×\dfrac{5}{5+1}=0.65$(公顷)
旱地:$0.78×\dfrac{1}{5+1}=0.13$(公顷)
(2)$0.65÷5×1=0.13$(公顷)
$4.8:6.4=3:4$
$4.8:3=6.4:4$
$6.4:4.8=4:3$
$3:4.8=4:6.4$
$3:4=4.8:6.4$
$4:6.4=3:4.8$
$4:3=6.4:4.8$
$6.4:4=4.8:3$
$8÷(9 - 7)=4$(棵) $4×(9 + 7)=64$(棵)