(1) $486+529$
$=(100×\_\_\_\_\_\_+10×\_\_\_\_\_\_+1×\_\_\_\_\_\_)+(100×\_\_\_\_\_\_+10×\_\_\_\_\_\_+1×\_\_\_\_\_\_)$
$=100×(\_\_\_\_\_\_+\_\_\_\_\_\_)+10×(\_\_\_\_\_\_+\_\_\_\_\_\_)+1×(\_\_\_\_\_\_+\_\_\_\_\_\_)$
$=100×(\quad)+10×(\quad)+1×(\quad)=(\quad)$
(2) $3.28+5.7$
$=(1×\_\_\_\_\_\_+0.1×\_\_\_\_\_\_+0.01×\_\_\_\_\_\_)+(1×\_\_\_\_\_\_+0.1×\_\_\_\_\_\_)$
$=1×(\_\_\_\_\_\_+\_\_\_\_\_\_)+0.1×(\_\_\_\_\_\_+\_\_\_\_\_\_)+0.01×(\quad)$
$=1×(\quad)+0.1×(\quad)+0.01×(\quad)=(\quad)$
(3) $\frac{2}{7}+\frac{3}{5}$
$=\frac{(\quad)}{35}\frac{(\quad)}{35}$
$=\frac{1}{35}×(\quad)+\frac{1}{35}×(\quad)$
$=\frac{1}{35}×(\_\_\_\_\_\_+\_\_\_\_\_\_)=(\quad)$

(1)
$486+529$
$=(100×\underline{4}+10×\underline{8}+1×\underline{6})+(100×\underline{5}+10×\underline{2}+1×\underline{9})$
$=100×(\underline{4}+\underline{5})+10×(\underline{8}+\underline{2})+1×(\underline{6}+\underline{9})$
$=100×(\underline{9})+10×(\underline{10})+1×(\underline{15})=(\underline{1015})$
(2)
$3.28+5.7$
$=(1×\underline{3}+0.1×\underline{2}+0.01×\underline{8})+(1×\underline{5}+0.1×\underline{7})$
$=1×(\underline{3}+\underline{5})+0.1×(\underline{2}+\underline{7})+0.01×(\underline{8})$
$=1×(\underline{8})+0.1×(\underline{9})+0.01×(\underline{8})=(\underline{8.98})$
(3)
$\frac{2}{7}+\frac{3}{5}$
$=\frac{(\underline{10})}{35}+\frac{(\underline{21})}{35}$
$=\frac{1}{35}×(\underline{10})+\frac{1}{35}×(\underline{21})$
$=\frac{1}{35}×(\underline{10}+\underline{21})=(\underline{\frac{31}{35}})$

4. 计算下面各题，注意使计算简便。
$136+302$
$8.3+0.15+0.85+1.7$
$\frac{7}{8}-\frac{4}{5}+\frac{1}{8}-\frac{1}{5}$

$136+302$
$=136+300+2$
$=436+2$
$=438$
$8.3+0.15+0.85+1.7$
$=(8.3+1.7)+(0.15+0.85)$
$=10+1$
$=11$
$\frac{7}{8}-\frac{4}{5}+\frac{1}{8}-\frac{1}{5}$
$=(\frac{7}{8}+\frac{1}{8})-(\frac{4}{5}+\frac{1}{5})$
$=1-1$
$=0$