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Byju's Answer
Standard X
Mathematics
Volume of a Frustum
The slant hei...
Question
The slant height of the frustum of a cone is 4 cm and the perimeters (i.e. circumferences) of its circular ends are 18 cm and 6 cm. Find the curved surface area of the frustum.
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Solution
Let R and r be the radii of the top and base of the frustum of the cone, respectively, and its slant height be l.
Then,
2
π
R
=
18
⇒
π
R
=
9
.
.
.
(
i
)
2
πr
=
6
⇒
πr
=
3
.
.
.
.
(
i
i
)
Curved surface area of the frustum
=
π
l
R
+
r
=
l
×
π
R
+
π
r
=
4
×
9
+
3
Since
l
=
4
cm
(
f
r
o
m
(
i
)
a
n
d
(
i
i
)
)
=
48
cm
2
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The slant height of the frustum of a cone is 4 cm and the perimeters of its circular ends are 18 cm and 6 cm. Find the curved surface of the frustum.