第78页 - 经纶学典学霸四年级数学上下册【江苏国标】

100010001

$~~~~ \underbrace{222···22}_{2000个2}×\underbrace{999···99}_{2000个9}$

$=\underbrace{222···22}_{2000个2}×(1\underbrace{000···00}_{2000个0}-1)$

$=\underbrace{222···22}_{2000个2}×1\underbrace{000···00}_{2000个0}-\underbrace{222···22}_{2000个2}$

$=\underbrace{222···2}_{1999个2}1\underbrace{77···7}_{1999个7}8$

=3×11111×3333

=11111×9999

=11111×(10000-1)

=111110000-11111

=111098889

2468

100010001

2000

135713571357×2468-1357×246824682468

=1357×100010001×2468-1357×2468×100010001

=0

$ \begin{aligned} &=9×\underbrace{111···11}_{99个1}×\underbrace{444···44}_{99个4}÷\underbrace{666···66}_{99个6} \\ &=9×\underbrace{111···11}_{99个1}×4×\underbrace{111···11}_{99个1}÷\underbrace{111···11}_{99个1}÷6 \\ &=6×\underbrace{111···11}_{99个1} \\ &=\underbrace{666···66}_{99个6} \\ \end{aligned}$