3.14×102= 3.14x(100+2)=3.14x100+3.14x2=314+6.28=320.280.125×7.41×80= 0.125x80x7.41=10x7.41=74.1(3.2+0.56)÷0.8=3.2÷0.8+0.56÷0.8=4+0.7=4.7