①39.9×9.9 ②400.009÷0.09
③799×0.5 ④12.5×40×0.81
2.5×4= 1.25×8= 0.56÷0.7= 0.45÷0.3=
3.6÷0.9= 14.3÷0.1= 15.8×0.1= 3.6÷0.9-4=