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Question
Find the cost of painting a hemispherical dome of diameter 10 m at the rate of Rs 1.40 per square metre.
Solution
Diameter of the hemispherical dome = 10 m
Therefore, radius of dome = 5 m
Curved surface area = `2pir^2`
= `2 xx 22/7 xx 5 xx 5`
= 157.14 m2
Cost of painting one sq. metre = Rs. 1.40
Cost of painting 157.14 m2 = Rs.(1.40 x 157.14)
= Rs. 219.99 = Rs 220
Therefore, cost of painting the dome = Rs 220
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