0.4-0.4+0.4-0.4=0
(0.4-0.4*0.4)/0.4+0.4=1
0.4÷[(0.4+0.4)÷0.4]=2
0.4÷0.4+(0.4+0.4)÷0.4=3
(0.4+0.4+0.4+0.4)÷0.4=4