Tub A is a frustum with top radius 20 cm and bottom radius 11 cm. Tub B has top radius 11 cm and bottom radius 20 cm. Both are 12 cm deep. Which tub holds more water?

The volume $\frac{1}{3}\pi h(R^2+r^2+Rr)$ is symmetric in $R$ and $r$ - swapping the two radii changes nothing. Both hold $\frac{1}{3}\pi \times 12\times (400+121+220)=2964\pi {\text{cm}}^3$. Which end is on top affects only how the tub is used, not its capacity, and the value chosen for $\pi$ scales both tubs equally.