Question

A hemispherical bowl has 3.5 cm radius. It is to be painted inside as well as outside. Find the cost of painting it at the rate of ₹15 per 10 cm². (Use ∏ = 22/7)

• A. ₹431
• B. ₹331
• C. ₹231
• D. ₹531

Answer 1

Answer:

C. ₹231

Radius (r = 3.5) cm

A hemispherical bowl painted inside and outside, so total surface area:

$\text{Total SA} = 2 \times (2\pi r^2) = 4\pi r^2$
Compute area

$4 \times \frac{22}{7} \times (3.5)^2$

$(3.5)^2 = 12.25$

$= 4 \times \frac{22}{7} \times 12.25$

$= 4 \times 22 \times 1.75$

$= 154 \text{ cm}^2$

Cost calculation

Rate = ₹15 per 10 cm²
So per 1 cm² = ₹1.5

$\text{Cost} = 154 \times 1.5 = 231$

Final Answer: ₹231