A cone of radius 14 cm height 15 cm is cut in a plane parallel to its base. If
the area of the circle at the intersection is 154 sqm then what is the height
from the base at which the cone is cut?
(a) 10cm
(b) 5 cm
(c) 15 cm
(d) 7.5 cm
Since area of circle with BC as radius is 154 sqcm
Π(BC)2 = 154
BC = 7 cm.
Triangles ABC and ADE are similar triangles.
AB/AD = BC/DE.
As BC = 7 and DE is 14 cm
BC/DE = 1/2
AB/AD must also be 1/2.
As AD = 15, AB must be 7.5 cm.
hence the answer is D