A hemispherical bowl made of brass has inner diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of ₹ 16 per 100 cm2.
Solution:
Hemisphere is exactly half of a sphere, so the curved surface area is half of the surface area of the sphere.
CSA of the hemisphere with radius r, CSA = 2πr2.
Since the bowl is to be tin-plated from inside, the area to be tin-plated will be equal to the CSA of the hemisphere.
Inner diameter, d = 10.5cm
Inner radius, r = 10.5/2cm = 5.25cm
CSA of hemispherical bowl = 2πr2
= 2 × 22/7 × 5.25cm × 5.25cm
= 173.25 cm2
The cost of tin-plating 100 cm2 of the bowl = ₹16
The cost of tin-plating 1 cm2 of the bowl = ₹16/100
The cost of tin-plating 173.25 cm2 area of the bowl = (₹16/100) ×173.25 = 27.72
Thus, the cost of tin-plating is ₹ 27.72.
☛ Check: NCERT Solutions for Class 9 Maths Chapter 13
Video Solution:
A hemispherical bowl made of brass has inner diameter 10.5 cm. Find the cost of tin-plating it on the inside at the rate of ₹ 16 per 100 cm².
Class 9 Maths NCERT Solutions Chapter 13 Exercise 13.4 Question 5
Summary:
It is given that a hemispherical bowl made of brass has an inner diameter of 10.5 cm. We have found that the cost of tin-plating it on the inside at the rate of ₹ 16 per 100 cm2 is ₹27.72.
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