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Question -

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.



Answer -

Given,

Radius of the conicalportion of the toy = 3.5 cm = r

Total height of thetoy = 15.5 cm = H

If H is the length ofthe conical portion

Then,

Length of the cone (h)= H – r = 15.5 – 3.5 = 12 cm

Now, we know that

The curved surfacearea of the cone (S1) = πrL, where L is the slant height of thecone.

L2 = r2 +h2

L2 =3.52 + 122

L2 =12.25 + 144 = 156.25

L = 12.5

So,

S1 = π(3.5)(12.5)

S1 =137.5 cm2

Next, the curved surfacearea of the hemisphere (S2) = 2πr2

S2 =2π (3.5)2

S2 =77 cm2

Therefore,

The total surface areaof the toy (S) = Curved surface area of the cone + curved surface area of thehemisphere

S = S1 +S2

S = 137.5 + 77

S = 214.5 cm2

Hence, the totalsurface area of the children’s toy is 214.5 cm

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