A.
16 cups equal 1 gallon.
First, convert 1 5/8 gallons into cups.
1 5/8 x 16 = (13/8) x (16/1) = 26 cups
For the colors, divide each color [2/5 red and 1/4 blue] by the total of both colors [2/5 + 1/4], then multiply by the value you are determining the ratio for [26 cups].
For red:
(2/5) / (2/5)+(1/4)=
(2/5) / (13/20) =
(2/5) x (20/13)= 8/13
(8/13) x 26 = 16 cups or 1 gallon
For blue:
(1/4) / (2/5)+(1/4)=
(1/4) / (13/20) =
(1/4) x (20/13)= 5/13
(5/13) x 26 = 10 cups or 10/16 of a gallon
10/16 simplifies to 5/8 gallon
Final answer: 1 gallon of red, 5/8 gallon of blue.