Question

31) The curved surface area of a frustrum of a cone having slant height 4 cm and radii of its circular bases 9/ π cm and 3/ π cm is A) 200 π cm2 B) 192 cm2 C) 96 cm2 D) 48 cm2​

Answer 1

Answer:

48 cm²

Step-by-step explanation:

Since, we know that the perimeter of a circular base having radius a unit is equal to (2πr).

• ⇒ 2πr = 6
• ⇒ πr = 3
• ⇒ r = 3/π

Also, 2πR = 18

• ⇒ πR = 9
• ⇒ R = 9/π

So, curved surface area

• = π × 4 × (9/π + 3/π)
• = π × 4 × (9 + 3/π)
• = π × 4 × (12/π)
• = 48 cm²

So, option D) is the correct Answer

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