The easiest way to do this is to write the decimals with equal amount of places after the dot and you'll see it more clearly:
1.09 = 1.090
1.901 = 1.901
1.9 = 1.900
1.19 = 1.190
So from the least to the greatest:
1.090
1.190
1.900
1.901
In a form you gave at the beginning:
1.09 < 1.19 < 1.9 < 1.901
