2.5×（0.4+0.8）×12.5怎么巧算

(2.5x0.4+2.5x0.8)x12.5=(1+2)x12.5=3x12.5=37.5

12.5*0.8+0.4*2.5=12.5x0.8x2.5+12.5x0.4x2.5=10x2.5+12.5x1=25+12.5=37.5

2.5*(0.4+0.8)*12.5=(1+ 2)*12.5=3*12.5=3.75

12.5*(0.4+0.8)*2.5=12.5*(0.4*2.5+0.8*2.5)=12.5*(1+2)=12.5*3=37.5 望采纳 谢谢

4*0.8*2.5*12.5 =4x2.5x(12.5x0.8) =10x10 =100 有不明白的可以追问!谢谢!! 祝学习进步!

答案:4.5 思路:小数化分数,将0.4 0.8 2.5 1.25化成分数:2/5 4/5 10/4 5/4 这样 前面括号相加是 6/5,后面括号相加是15/4.相乘一约分就是4.5

(0.4+0.8)*2.5*12.5 =0.4*2.5*12.5+0.8*12.5*2.5 =12.5+25 =37.5.

2.5*12.5*0.8*0.4=12.5*0.8*2.5*0.4=10x1=10

0.8*(2.5+1.25)*0.4=0.8*(2.5*0.4+1.25*0.4)=0.8*(1+0.5)=0.8+0.4=1.2 或者0.8*(2.5+1.25)*0.4=0.8*(2.5*0.4)+(0.8*1.25)*0.4=0.8+0.4=1.2

=0.4x15x0.8 =0.4x3x5x8 =2x3x8 =48