Question

7.5x2.3+1.9x2.5+22.5x0.4怎样用简便运算?

Answer 1

7.5x2.3+1.9x2.5+22.5x0.4
=7.5×（2.5-0.2）+1.9×2.5+（20+2.5）×0.4
=7.5×2.5-7.5×0.2+1.9×2.5+20×0.4+2.5×0.4
=7.5×2.5+1.9×2.5+0.4×2.5-7.5×0.2+20×0.4
=2.5×（7.5+1.9+0.4）-1.5+8
=2.5×（10-0.2）+6.5
=25--0.5+6.5
=31

Answer 2

7.5=2.5×3
22.5=2.5×9
所以就变成
2.5×(3×2.3+1.9+9×0.4)=2.5×(6.9+1.9+3.6)=25×12.4=31

Answer 3

7.5x2.3+1.9x2.5+22.5x0.4
=7.5*(1.9+0.4)+1.9x2.5+22.5x0.4
=7.5*1.9+7.5*0.4+1.9x2.5+22.5x0.4
=7.5*1.9+1.9*2.5+(7.5*0.4+22.5*0.4)
=1.9*(7.5+2.5)+0.4*(7.5+22.5)
=1.9*10+0.4*30
=19+12
=31