Question

the front compound wall of a house is decorated by wooden spheres of diameter 21 cm placed on small support eight such sphere are used for this pupose and are to be painted silver each support is a cylinder of radius 1.5 cm nd height 7cm and is to be painted black . find the cost of paint required if silver paint costs 25 paise per cm square and black paint costs 5 paise per cm square (agar batoo to mano)

Answer 1

Radius of wooden sphere = 10.5 cm
SA of wooden sphere = 1386 cm²
 radius of cylindrical support = 1.5
height = 7 cm
so, CSA = 66 cm²
and area of circular end of cylindrical support = 7.07 cm²
area to be painted silver = 8 * (1386 - 7.07) = 11031.44 cm²
cost of painting with silver = 11031.44 * 0.25 = RS.2757.86
painting black = 528 * 0.05 =RS 26.40
total cost = 2757.86 + 26.40 = RS. 2784.26 

Answer 2

area of circular end of cylindrical support = 7.07 cm²
area to be painted silver = 8 * (1386 - 7.07) = 11031.44 cm²
cost of painting with silver = 11031.44 * 0.25 = RS.2757.86
painting black = 528 * 0.05 =RS 26.40
total cost = 2757.86 + 26.40 = RS. 2784.26