We need an equation for this, theres no 'formula' for doing this (ignoring the quadratic formula, as that is a long-winded way of factorising a quadratic equation)
All cone-shaped cups have the same height in 8 inches. They just differ in their diameters. To solve for the volume of the regular and jumbo sizes, let's use the formula for the volume of cone
V = (1/3)*pi*(r^2)*h
r is just the half of the diameter, h is the height which is equal to 8
Regular size: V = (1/3)*pi*((4/2)^2)*8 V = 33.5 cube inches
Jumbo size: V = (1/3)*pi*((8/2)^2)*8 V = 134.0 cube inches
