25×3.9+2.5简便运算,快!
=25×3.9+25×0.1
先采纳
100
2.5*39+2.5=2.5*40
=25*4-25*0.1+2.5=50-2.5+2.5=50
=25x1一2,5x0,1
=25x(4-0.1)+2.5=25x4-25x0.1+2.5=100-2.5+2.5=100