5ᠧ999+5ᠧ99ᠧ7+7+3ᠧ9+3+9简便算法怎么算？

5✘999+5✘99✘7+7+3✘9+3+9简便算法怎么算？
=5*111*9+5*11*9*7+3*9+3+9
=5*9*(111+11*7)+27+3+9
=45*(111+77)+39
=45*188+39
=45*(100+80+8)+39
=45*100+45*80+45*8+39
=4500+3600+360+39
=8100+399
=8499

5×999+5×99×7+7+3×9+3+9
=5×9×111+5×7×9×11+7+27+3+9
=45×111+45×77+(27+3)+(7+9)
=45×(111+77)+30+16
=45×188+45×1+1
=45×(188+1)+1
=45×189+1
=45×(200-11)+1
=45×200-45×11+1
=9000-495+1
=9000-(500-5)+1
=9000-500+5+1
=8500+6
=8506
一个数乘以11的简便计算方法是，“两边一拉，中间相加”。如43×11=473。

5*999+5*99*7+7+3*9+3+9
=5*999+35*99+7+27+3+9
=5*999+35*99+35+5+6
=(5*999+5)+(35*99+35)+6
=5000+3500+6
=8506

5✘999+5✘99✘7+7+3✘9+3+9
=(5✘999+5✘99✘7+3✘9+9)+7+3
=9x(555+55x7+3+1)+10
=9x(559+385)+10
=9x944+10
=(10-1)x944+10
=9440-944+10
=9440-934
=8506