24 3/4 = 18
The radius of smaller cone is 3/4 the radius of original cone, so since these cones are similar, height must also be 3/4 times smaller.
So since radius is squared and we also multiple the height (V = 1/3 π r² h),
the volume of smaller cone would be 3³ / 4³ = 27 / 64 times smaller
So we have 1920 (27 / 64) = 810.
Final answer: B
