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Question
CBSEENMA10008931

Mayank made a bird-bath for his garden in the shape of a cylinder with a hemispherical depression at one end. The height of the cylinder is 1.45 m and its radius is 30 cm. Find the total surface area of the birth - bath.   

open parentheses bold pi bold space bold equals bold space bold 22 over bold 7 close parentheses bold space bold space


Solution

Let r cm be the radius and h cm be the height of the cylinder then,
r = 30 cm,
h = 1.45 m = 145 cm.
Lei r1 cm be the radius of the hemisphere, then
r1 = 30 cm
Now,
The Total Surface Area of the bird bath
= C.S.A of cylinder + C.S.A of Hemisphere
= 2 straight pi rh + 2 straight pi r1 2
= 2straight pirh + 2straight pir2    [∵ r = r1]
= [2 ∵ r (h + r)] cm2

equals space open square brackets open parentheses 2 straight x 22 over 7 straight x 30 close parentheses left parenthesis 145 space plus space 30 right parenthesis close square brackets space cm squared
equals space open parentheses 1320 over 7 straight x 175 close parentheses space cm squared
= 33000 cm2
= 3.3 m2

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