用简便方法计算:1.1.1+2.2+3.3+4.4+5.5+6.6+7.7+8.8+9.9 2.14.5+6.65*39.9+25.4+2.35*39.9是两题
问题描述:
用简便方法计算:1.1.1+2.2+3.3+4.4+5.5+6.6+7.7+8.8+9.9 2.14.5+6.65*39.9+25.4+2.35*39.9
是两题
答
1.原式=(1+2+--+9)+(0.1+0.2+--+0.9)=(1+2+--+9)*1.1=49.5
2.原式=39.9*(1+6.65+2.35)=39.9*10=399