NCERT Solutions for Class 9 Maths Chapter 13
Important NCERT Questions
Surface Areas and Volumes
NCERT Books for Session 2022-2023
CBSE Board, UP Board and Other state Boards
EXERCISE 13.4
Page No:225
Questions No:5
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 Rs 16 per 100 cm².
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Internal radius of hemispherical bowl r = 10.5/2 = 5.25 cm
Inner surface area of hemispherical bowl = 2πr²
= 2 × 22/7 × 5.25 × 5.25
= 2 × 22 × 0.75 × 5.25
= 173.25 cm²
Cost of tin-plating the rate of Rs 16 per 100 cm²
= Rs 173. 25 × 16/100 = Rs 27.72
Hence, the cost of tin- plating inside at the rate of Rs 16 per 100 cm² is Rs 27.72.