where r = radius and h = height

since it is split in 2 parts with equal height k

the height of the big cone is h = 2k

so

V = (1/3)πr^2(2k) = (2/3)πr^2k is the volume of the big cone

now

the top portion is a cone with radius = r/2 and height = k

so

v = (1/3)π(r/2)^2k = (1/3)π(r^2 /4)k = (1/12)πr^2k

then the volume of the bottom portion is the

volume of the big cone minus the volume of the top cone

ie

V-v = (2/3)πr^2k – (1/12)πr^2k

= (2/3 – 1/12)π(r^2)k

= (7/12)π(r^2)k

is the volume of the bottom portion

so

ratio = (V-v) / v = 7/1

or 7:1

the bottom portion is 7 times the volume of the top portion

.