$V = \frac{1}{3}(A_1 + A_2 + \sqrt{A_1\,A_2}) ~ h$
Where,
$A_1 = \frac{1}{4}\pi(5.75^2) = \frac{529}{64}\pi ~ \text{in.}^2$
$A_2 = \frac{1}{4}\pi(4.5^2) = \frac{81}{16}\pi ~ \text{in.}^2$
$h = 5 ~ \text{in.}$
Hence,
$V = \frac{1}{3}[ \, \frac{529}{64}\pi + \frac{81}{16}\pi + \sqrt{\frac{529}{64}\pi(\frac{81}{16}\pi)} \, ] ~ (5)$
$V = \frac{6335}{192}\pi ~ \text{in.}^3 = 103.66 ~ \text{in.}^3$
$V = \frac{6335}{192}\pi ~ \text{in.}^3 \times \dfrac{1 ~ \text{gal}}{231 ~ \text{in.}^3} \times \dfrac{4 ~ \text{quarts}}{1 ~ \text{gallon}}$
$V = 1.795 ~ \text{quarts}$
Number of cups
$n = 1.795 ~ \text{quarts} \times \dfrac{6 ~ \text{cups}}{1 ~ \text{quart}}$
$n = 10.77 ~ \text{say} ~ 11 ~ \text{cups}$ answer
