4.9=7*0.7 1.4=7*0.2 即0.7/0.2=3.5
4.9/1.4分子分母同除以7=0.7/0.2=3.5
4.9÷1.4=(0.7*7)÷(0.2*7)=0.7*7÷0.2÷7=0.7÷0.2*(7÷7)=0.7÷0.2=3.5
4.9*1.4=(5-0.1)*1.4=5*1.4-0.1*1.4=7-0.14=6.86
原式=(4.9÷0.7)÷(1.4÷0.7) =7÷2 =3.5
4.9÷1.4=4.9÷0.7÷2=7÷2=3.5
展开全部4.9/1.4=49/14=49/7/2=7/2=3.5
4.9*1.42.1*0.7=9.8*0.7-2.1*0.7=0.7*(9.8-2.1)=0.7*7.7=5.39
4.9+5.2*1.4=4.9+5x1.4+0.2x1.4=4.9+7+0.28=11.8+0.28=12.08
4.9除以1.4=(7*0.7)除以(2*0.7)=7除以2=3.5