简便运算:1.9+19.9+199.9+1999.9+0.4=

问题描述:

简便运算:1.9+19.9+199.9+1999.9+0.4=

原式=(2-0.1)+(20-0.1)+(200-0.1)+(2000-0.1)+0.4 =2+20+200+2000-0.4+0.4 =2222