55×66+66×77+77×88+88×99 简便算法是?要按这样写:= = =

问题描述:

55×66+66×77+77×88+88×99 简便算法是?要按这样写:= = =

=11*11*(5*6)+11*11*(6*7).+11*11*(8*9)
=121*(30+42+56+72)
=121*200
=24200