# Q : 2     The front compound wall of a house is decorated by wooden spheres of diameter 21 cm, placed on small supports as shown in Fig . Eight such spheres are used for this purpose, and are to be painted silver. Each support is a cylinder of radius and height 7 cm and is to be painted black. Find the cost of paint required if silver paint costs 25 paise per and black paint costs 5 paise per .

Given,

The radius of the wooden spheres =

The surface area of a single sphere =

Again, the Radius of the cylinder support =

Height of the support =

The base area of the cylinder =

Now, Cost of painting silver =

Cost of painting 1 wooden sphere = Cost of painting silver

Now, Curved surface area of the cylindrical support =

Now, Cost of painting  black =

Cost of painting 1 such stand = Cost of painting silver =

The total cost of painting 1 sphere and its support =

Therefore, total cost of painting 8 such spheres and their supports =

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