解0.32x25x12.5=0.4×0.8x25x12.5=0.4x25x12.5×0.8=(0.4x25)x(12.5×0.8)=10×10=100对
0.32x25x12.5=0.8×0.4×25×12.5 =0.8×12.5×（0.4×25） =10×10 =100
