解: 3.28*0.75+1.72*3/4=3.28*0.75+1.72*0.75=0.75*(3.28+1.72)=0.75*5=3.75
＝3.28×3/4+1.72×3/4＝（3.28+1.72）×3/4＝5×3/4＝15/4＝3.75
