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CBSE Class 9 Answered

A hemispherical dome of a fort needs to be polished. If the circumference of the base of the dome is 27.72 m, find the cost of polishing it at the rate of Rs 25 per 1000 cm2.
Asked by Topperlearning User | 18 Oct, 2017, 03:10: PM
answered-by-expert Expert Answer

Let r= radius of the base of a hemispherical tomb.

Circumference of the base = 27.72 m=2772 cm

 

begin mathsize 12px style 2 πr space equals space 2772 space cm straight r space equals space fraction numerator 2772 cross times 7 over denominator 2 cross times 22 end fraction straight r space equals space 441 space cm end style

begin mathsize 12px style Lateral space surface space area space equals space 2 πr squared equals 2 cross times 22 over 7 cross times 441 squared space equals space 1222452 space cm squared end style

Cost of polishing 1000 cm2 = Rs 25

Therefore, cost of polishing 1222452 cm2 = Rs

                                                            = Rs 30561.30

Answered by | 18 Oct, 2017, 05:10: PM

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