If the height of a cone is tripled and radius is held constant, then the volume will double
If the height is tripled and the radius is unchanged, the volume will triple.
To see this.....note that a cross-section of the cone will form a triangle. And triangles on the same bases are to each other as their heights. So, the triangle cross-section of the cone with its height tripled will have 3 times the area of the cone without its height tripled. And the sum of all these cross sections will form a volume three times of that of the sum of all the cross-sections of the cone with the "normal" height.
If the height is tripled and the radius is unchanged, the volume will triple.
To see this.....note that a cross-section of the cone will form a triangle. And triangles on the same bases are to each other as their heights. So, the triangle cross-section of the cone with its height tripled will have 3 times the area of the cone without its height tripled. And the sum of all these cross sections will form a volume three times of that of the sum of all the cross-sections of the cone with the "normal" height.