Given:

Outer diameter (D) = 17cm

Inner diameter (d) = 15cm

Cost of polishing it per cm² = ₹2.50

To find:

Total surface of the hemispherical bowl.

The cost of polishing it all over at Rs 2.50 per cm²

Solution:

First we will find the C.S.A. of inner bowl

So, this implies 2πr²

2×22/7×(15)²

44/7×225

1414.3 cm²

Also the C.S.A of outer bowl = 2πR²

So, this implies 2×22/7×(17)²

44/7×289

1816.6 cm²

Now, the area of its ring = 2π(R-r)²

So, this implies 2×22/7×(17-15)²

44/7×(2)²

44/7×4

176/7

25.1 cm²

Now, Total surface area of the hemispherical bowl = C.S.A. of the outer bowl + C.S.A. of the inner bowl + Area of its ring

So, this implies 1414.3 + 1816.6 + 25.1 = 3256 cm²

So, The cost of polishing 3256 cm²= ₹2.50×3256

= ₹8,140

Hence the cost of polishing it all over = ₹8140

Hope it helps you.

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