21 ÷ 128 = 0.164063
-184
8
2
128
8
21.3333
128
128
21.3333
-133
128
One gallon contains 128 fluid ounces. 6 (ounces in your glass) divided by 128 (ounces in a gallon)=0.047. There is 0.047, or roughly one twentieth, of a gallon in one six ounce glass. Conversely, there are (128 divided by 6)=21 and one third (21.33) six ounce glasses of liquid in a gallon of it.