A hemispherical bowl is made of a stell, 0.25 cm thick. The inner radius of the bowl is 5 cm. Find the cost of painting it, given tha rate of painting is rs 5 per 100 cm2
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We want to paint the entire bowl.
Surface area of a hemisphere is as follows :
Sa = 2πr²
we have the inner side and the outer side :
The radius of the outer bowl is :
5 + 0.25 cm = 5.25 cm
Inner area = 2 × 3.14 × 5² = 157 cm²
Outer area = 2 × 5.25² × 3.14 = 173.0925 cm²
The top part is in form of a circle.
we need to get the area of the edge too.
area of a circle = πr²
the area of the edge = (3.14 × 5.25²) - (3.14 × 5²) = 8.04625 cm²
Total area :
8.04625 + 173.0925 + 157 = 338.14 cm²
The cost of painting is :
338.14/100 × 5 = 16.907
Rs 16.907
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