A hemispherical bowl made of brass has an inner radius 3.5 cm. Find the cost of tin plating it on the inside at the rate of Rs. 4 per cm².

Correct option is A

Given:

Inner radius of hemispherical bowl = 3.5 cm

Rate of tin plating = ₹4 per cm²

Formula Used:

CSA of hemisphere = $$2\pi r^2$$​​

Solution:

CSA of hemisphere = $$2 \times \frac{22}{7} \times (3.5)^2$$​​

= $$2 \times \frac{22}{7} \times \frac{49}{4}$$​​

= $$\frac{44 \times 49}{28} = \frac{2156}{28} = 77.0\ \text{cm}^2$$​​

Cost = 77 × 4 = ₹308