这题用简便方法怎么做32.2乘以0.4加178乘以0.044.83乘以7.5加75乘以0.51要有步骤用简便方法

32.2*0.4+178*0.04=32.2*0.4+17.8*0.4=0.4*（32.2+17.8）＝0.4*50=20
4.83*7.5+75*0.51=7.5*（4.83+5.1）＝7.5*9.93＝7.5*10-7.5*0.07=75-0.525＝74.475