1.2×2= 0.5×0.4= 0.56×1= 300×0.6=
2.8÷0.4= 0.123÷0.03= 0.56×0.7= 4÷8=
①0.75+0.25×2
②5.5×17.3-7.3×5.5
③3.8+4.29+5.71+4.2
④0.23×2.5×4
⑤7.8÷(1.3×0.3)
理由: