Austin is using a funnel shown to fill a glass bottle with colored sand estimate the volume of the funnel number 21

The volume of a frustum of a cone is given by
.. V = (1/3)*π*h*(R^2 +r^2 +R*r)
We will assume the diameter at the bottom is 1 1/2 inch. Then the slanted part has volume
.. V = (1/3)*π*4*(2.5^2 +.75^2 +2.5*.75) ≈ 36.39 . . . . in^3

The volume of the 1-inch cylinder at the bottom is
.. V = π*(1/2)^2*1 = π/4 ≈ 0.79 . . . . in^3

Then the total volume of the cone is approximately 37.18 in^3.