3.2x0.25x12.5=(4x0.8)x0.25x12.5=(4x0.25)(0.8x12.5)=1x10=10
3.2*0.25*12.5=（0.8*4）*0.25*12.5=（0.8*12.5）*（4*0.25）=10*1=10
