Question

5. The dome of a building is in the form of a
hemisphere. Its radius is 4.2 m. Find the cost
of painting it at the rate of 18 per m2.​

Answer 1

Answer:

The required cost of painting is ₹1995.84

Step-by-step explanation:

Given :

The dome of a building is in the form of a hemisphere. Its radius is 4.2 m.

To find :

the cost of painting it at the rate of ₹18 per m².

Solution :

The curved surface area of the hemisphere = 2πr²

  where r is the radius of the hemisphere

As given, r = 4.2 m

So, C.S.A of the dome of the building :

 $\sf = 2 \times \dfrac{22}{7} \times 4.2 \times 4.2 \\\\ \sf = 44 \times 4.2 \times 0.6 \\\\ \sf = 110.88 \: m^2$

The rate of painting is ₹ 18/m².

Total cost of painting = C.S.A of the hemisphere × rate of painting

    = 110.88 × 18

     = ₹1995.84

∴ The required cost of painting is ₹1995.84