A toy is in the form of a cone of radius 3.5 cm mounted on a hem

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411. A toy is in the form of a cone of radius 3.5 cm mounted on a hemisphere of same radius. The total height of the toy is 15.5 cm. Find the total surface area of the toy.


Let r cm be the radius, h cm be the height and l cm be the slant height of the cone, then


Let r cm be the radius, h cm be the height and l cm be the slant heig

r = 3.5 cm,
h = (15.5 – 3.5) cm = 12 cm.

Now,   l = square root of straight r squared plus straight h squared end root
rightwards double arrow space space straight l space equals space square root of left parenthesis 3.5 right parenthesis squared plus left parenthesis 12 right parenthesis squared end root
space space space space space space space equals space square root of 12.25 plus 144 end root
space space space space space space space equals space square root of 156.25 end root
space space space space space space space equals space 12.5 space cm.
space space space space space space space space

 Let r1 cm be the radius of the hemisphere.
Then, r1 = 3.5 cm    [∵ r = r1]
Now,
The total surface area of the toy
= CSA of hemisphere
+ CSA of cone
= 2 π r12 + πrl
= 2π r2 + πrl    [ ∵ r1= r]
= π r [2r + l]

equals space 22 over 7 space straight x space 3.5 space left square bracket 2 space straight x space 3.5 space plus space 12.5 right square bracket
equals space space left square bracket 11 space left parenthesis 7 space plus 12.5 right parenthesis right square bracket space cm squared
equals space space left square bracket space 11 space straight x space 19.5 right square bracket space cm squared space equals space 214.5 space cm squared
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419.

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Fig. 13.17.

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