Q9.    A wooden article was made by scooping out a hemisphere from each end of a solid cylinder, as shown in Fig. 13.11. If the height of the cylinder is 10 cm, and its base is of radius 3.5 cm, find the total surface area of the article.

                    

Answers (1)

The required surface area is given by  :

                  Surface area of article   =   Surface area of cylindrical part  +  2 (Surface area of hemisphere)

Now, area of cylinder   =\ 2\pi rh

or                                 =\ 2\pi \times 3.5\times 10

or                                =\ 70\pi \ cm^2

And the surface area of hemisphere :  =\ 2\pi r^2

or                                                         =\ 2\pi \times 3.5\times 3.5

or                                                         =\ 24.5\pi\ cm^2

Thus the required area   =\ 70\pi\ +\ 2(24.5\pi)\ =\ 374\ cm^2

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