3.7×1.83.7 4.2÷1.54.2 6.21÷0.016.21×100
7.5÷1.57.5 39.6÷36.91
258÷0.625.8÷0.06 9.9×1.01 9.9÷1.01
① a×0.6 ② a÷0.6 ③ a×0.8 ④ a÷0.8