Solution:
Diameter of wooden sphere = 21 cm
Radius of wooden sphere, r = diameter/ 2 = (21/2) cm = 10.5 cm
Formula: Surface area of wooden sphere = 4Ï€r2
= 4×(22/7)×(10.5)2 = 1386
So, surface area is 1386 cm3
Radius of the circular end of cylindrical support = 1.5 cm
Height of cylindrical support = 7 cm
Curved surface area = 2Ï€rh
= 2×(22/7)×1.5×7 = 66
So, CSA is 66 cm2
Now,
Area of the circular end of cylindrical support = πr2
= (22/7)×1.52
= 7.07
Area of the circular end is 7.07 cm2
Again,
Area to be painted silver = [8 ×(1386-7.07)] = 8×1378.93 = 11031.44
Area to be painted is 11031.44 cm2
Cost for painting with silver colour = Rs(11031.44×0.25) =Rs 2757.86
Area to be painted black = (8×66) cm2 = 528 cm2
Cost for painting with black colour =Rs (528×0.05) = Rs26.40
Therefore, the total painting cost is:
= Rs(2757.86 +26.40)
= Rs 2784.26
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