The ratio of radius and height of a cylinder is 5 ∶ 7 and its volume is 550 cm3. Calculate the curved surface area.

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  1. 500 cm2
  2. 196 cm2
  3. 321 cm2
  4. 220 cm2

Answer (Detailed Solution Below)

Option 4 : 220 cm2
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Detailed Solution

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Given:

The ratio of radius and height of a cylinder is 5 ∶ 7

Volume (V) = 550 cm3

Formula used:

Volume of a cylinder, V = πr2h

Curved Surface Area (CSA) = 2πrh

Calculation:

Let the radius (r) = 5k and height (h) = 7k

Volume, V = πr2h

⇒ 550 = π(5k)2(7k)

⇒ 550 = 22/7 × 25k2 × 7k

⇒ 550 = 550k3

⇒ k3 = 1

⇒ k = 1

Therefore, r = 5 × 1 = 5 cm and h = 7 × 1 = 7 cm

Curved Surface Area, CSA = 2πrh

⇒ CSA = 2 × 22/7 × 5 × 7

⇒ CSA = 220 cm2

∴ The correct answer is option (4).

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