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# Solution for A Hemi-spherical Dome of a Building Needs to Be Painted. If the Circumference of the Base of the Dome is 17.6 Cm, Find the Cost of Painting It, Given the Cost of Painting is Rs. 5 per L00 Cm^2 - CBSE Class 9 - Mathematics

ConceptSurface Area of a Sphere

#### Question

A hemi-spherical dome of a building needs to be painted. If the circumference of the base of
the dome is 17.6 cm, find the cost of painting it, given the cost of painting is Rs. 5 per l00
cm^2

#### Solution

Given that only the rounded surface of the dome to be painted, we would need to find the
curved surface area of the hemisphere to know the extent of painting that needs to be done.
Now, circumference of the dome =17.6m.
Therefore, 17.6=2πr.

2× 22/7r= 17.6m.

So, the radius of the dome = 17.6× 7/(2× 22)

m=2.8m

The curved surface area of the dome = 2πr^2

=2× 22/7× 2.8× 2.8cm^2

= 49.28m^2

Now, cost of painting 100cm^2 is Rs. 5.

So, cost of painting 1m^2= Rs.500

Therefore, cost of painting the whole dome
=Rs. 500×49.28
=Rs. 24640 .

Is there an error in this question or solution?

#### APPEARS IN

Solution A Hemi-spherical Dome of a Building Needs to Be Painted. If the Circumference of the Base of the Dome is 17.6 Cm, Find the Cost of Painting It, Given the Cost of Painting is Rs. 5 per L00 Cm^2 Concept: Surface Area of a Sphere.
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