A hemispherical bowl has a 21 cm radius. It is to be painted inside as well as outside. The cost of painting it at the rate of ₹0.05 per cm² and assuming that the thickness of the bowl is negligible, is:(Use \(\pi=\frac{22}{7}\))

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Question

This question was previously asked in

SSC Selection Post 2024 (Higher Secondary Level) Official Paper (Held On: 24 Jun, 2024 Shift 2)

Answer 1

Given:

Radius (r) = 21 cm

Cost per cm² = ₹0.05

π = 22/7

Formula used:

Surface Area (SA) of a hemisphere = 2πr²

Total Surface Area (inside + outside) = 2 × SA

Calculation:

SA (inside) = 2 × (22/7) × 21²

⇒ SA (inside) = 2 × (22/7) × 441

⇒ SA (inside) = 2772 cm²

Total SA = 2 × 2772 cm²

⇒ Total SA = 5544 cm²

Cost = Total SA × ₹0.05

⇒ Cost = 5544 × 0.05

⇒ Cost = ₹277.20

∴ The cost of painting the bowl is ₹277.20

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