The internal and external diameters of a hollow hemispherical vessel are 20 cm and 28cm respectively. Find the cost of painting the vessel all over at 35 paise per cm².

Sure, here are the steps to solve the problem:

Step 1: Calculate the external surface area of the hemisphere. The formula for

Sure, here are the steps to solve the problem:

Step 1: Calculate the external surface area of the hemisphere. The formula for the surface area of a hemisphere is 2πr². Here, the external radius (r) is 14 cm (half of the diameter). So, the external surface area is 2π(14)² = 1232 cm².

Step 2: Calculate the internal surface area of the hemisphere. The internal radius is 10 cm. So, the internal surface area is 2π(10)² = 628 cm².

Step 3: Calculate the total surface area to be painted. The total surface area is the sum of the external and internal surface areas. So, the total surface area is 1232 cm² + 628 cm² = 1860 cm².

Step 4: Calculate the cost of painting. The cost of painting is 35 paise per cm². So, the total cost is 1860 cm² * 35 paise/cm² = 65100 paise.

Step 5: Convert the cost to rupees. 1 rupee = 100 paise. So, the total cost in rupees is 65100 paise / 100 = 651 rupees.

So, the cost of painting the vessel all over is 651 rupees.