分数的巧算 3.51*49+35.1*5.1+49*51 0.7*1又4/9+2又3/4*15+0.7*5/9+1/4*15

3.51*49+35.1*5.1+49*51 =3.51*49+3.51*51+（50-1）×51=3.51×（49+51）+50×51-51=351+2550-51=2850 0.7*1又4/9+2又3/4*15+0.7*5/9+1/4*15=0.7×（1又4/9+5/9）+15×（2又3/4+1/4 ）=0.7×2+15×3=1.4+45=46.4...