Question : The radius of the ends of a frustum of a solid right-circular cone 45 cm high is 28 cm and 7 cm. If this frustum is melted and reconstructed into a solid right circular cylinder whose radius of base and height are in the ratio 3: 5, find the curved surface area (in
Option 1: 4580
Option 2: 4610
Option 3: 4640
Option 4: 4620
Correct Answer: 4620
Solution :
According to the question,
Area of the frustum = Volume of the cylinder
⇒
⇒
⇒ (49 + 754 + 196) 15 =
⇒ 1029 =
⇒
⇒
Curved surface area =
= 2
= 2 × 22 × 5 × 21
= 4620
Hence, the correct answer is 4620.