me slant height of a frustum of a cone is 4 cm and
the perimeters (circumference) of its circular ends
are 18 cm and 6 cm. Find the curved surface area of
the frustum.
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Answer:
the curved surface area of the frustum of cone is 24 centimetre square
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Given,
Slant height of frustum of cone (l) = 4 cm
Let ratio of the top and bottom circles be r1 and r2
And given perimeters of its circular ends as 18 cm and 6 cm
⟹ 2πr1 = 18 cm; 2πr2 = 6 cm
⟹ πr1= 9 cm and πr2 = 3 cm
We know that,
Curved surface area of frustum of a cone = π(r1 + r2)l
= (πr1+πr2)l = (9 + 3) × 4
= (12) × 4 = 48 cm2
Therefore, the curved surface area of the frustum = 48 cm2.
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