第39页 - 通城学典课时作业本五年级数学苏教版江苏专用

$=\frac {7}{8}-\frac {7}{8}+\frac {8}{9}$

$=0+\frac {8}{9}$

$=\frac {8}{9}$

$=\frac {10}{9}-(\frac {4}{15}+\frac {11}{15})$

$=\frac {10}{9}-1$

$=\frac {1}{9}$

$=(\frac {3}{7}+\frac {11}{7})-(\frac {8}{13}+\frac {4}{13})$

$=2-\frac {12}{13}$

$=1 \frac {1}{13}$

$=(4.37+5.73)+(\frac {29}{24}-\frac {5}{24})$

$=10.1+1$

$=11.1$

$ \begin{aligned}解：x&=\frac {1}{3}+\frac {4}{7} \\ x&=\frac {19}{21} \\ \end{aligned}$

$ \begin{aligned}解：35x&=420 \\ x&=12 \\ \end{aligned}$

$ \begin{aligned}解：1.6x&=25.6×0.5 \\ 1.6x&=12.8 \\ x&=8 \\ \end{aligned}$

20×16−3.14×(16÷2)²=119.04(m²)

$20×π÷2=10π(\mathrm {cm}) $

$\frac {30}{360}=\frac {1}{12} $

$2×π×20÷12=\frac {10π}{3}(\mathrm {cm})$

$10π+\frac {10π}{3}+20=(\frac {40π}{3}+20)\mathrm {cm}$

3

20

30

12千米/时