The sequences with a common ratio of 1/4 are: 512, 128, 32, 8, ... 256, 64, 16, 4, ... 320, 80, 20, 5, ... 768, 192, 48, 12, ... 560, 140, 36, 9, ...
The others have a common ratio of 4.
The common ratio is found by dividing the second term by the first term. For instance, in the first sequence, we would have 28/7 = 4. In the second sequence, we have 128/512 = 1/4.
The flour-sugar total is 3 2/3 cups, of which 1/4 cup is sugar. So, to find the amount of flour used, we subtract 1/4 cup (sugar) from the total (3 2/3 cups):
11 1
----- - ---- where 11/3 is the improper fraction form of 3 2/3
3 4
The LCD is 12. Rewriting this subtraction using the LCD, we get: