A table lamp is in the shape of a glasshemisphere basesurmounted by a metalliccylindrical top of same radius 21cm and height 3.5cm.The top was silver coated and the glasssurface was painted red.what is cost of silvercoating the top at the rate of ₹5 per 200sq cm? What is the surface are of glass tobe painnted red?
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surface area to be painted red = 2772cm2
Step-by-step explanation:
Area to be coated with silver = 2πrh+πr2=πr(2h+r)
=22/7×21(7+21)
=66×28
=1848cm²
Cost of silver coating=1848/100 × 5
=92.5Rs
Surface area to be painted red = 2πr²
=2×22/7×21×21
=2772cm²
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