Height of the cone is 30 cm.
Let the height of the cone cut off be h cm
Δ ABE ∼ Δ ACD
Therefore
.............(1)
Volume of the small cone =
th volume of the given cone
×
=
×
×
=
×
(r/R)
2 h = 30 ´
(h/H)
2 h = 30 ´
..........[using (1)]
h
3 = 30 × 30 × 30 ´
h = 30/3 = 10 cm
Therefore the height of the above section is (30 - 10) cm = 20 cm.