2.4×7.5×1.25＝3×0.8×7.5×1.25＝（3×7.5)×（1.25×0.8）＝22.5×1＝22.5
2.4*7.5*1.25=0.3*7.5*（8*1.25）=2.25*10=22.5
2.4x7.5x1.25 =（0.3×8）×7.5×1.25 =（8×1.25）×0.3×7.5 =10×0.3×7.5 =3×7.5 =22.5
