四年级(下)巧算题28*1111+9999*8怎样巧算?急切!1

28*1111+1111*72
=(28+72)*1111
=100*1111
=111100

[28*(1000+111)=28000+20*111+8*111]+8*9999=28000+22200+80000

28*1111+9999*8
=28*1111+8*9*1111
=28*1111+72*1111
=(28+72)*1111
=100*1111
=111100

28*1111+9999*8
=28*1111+1111*9*8
=28*1111+72*1111
=(28+72)*1111
=100*1111
=111100