5.5x9.9+0.1x5.5 =(9.9十0.1)X5.5=100x5.5=550
原式=5.5*(9.9+0.1)=5.5*10=55
=5.5×(9.9+0.1)=5.5×10=55
原式=(9.9+0.1)×5.5=10×5.5=55