4.5x5.5+5.5x5.5=5.5x（4.5+5.5）=5.5x10=55
=5.5(4.5+5.5)=5.5*10=55
4.5×5.5+5.5×5.5=（4.5+5.5）×5.5=10×5.5=55
＝（4.5+5.5）*5.5＝10*5.5＝55
