I would like to give a question which

i could not solve.Rd sharma class 10

maths exercise-16.2 mensuration.

In this question we have to find the total surface

area of the toy given that 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.

Given,

Radius of the conical portion of the toy = 3.5 cm = r

Total height of the toy = 15.5 cm = H

If H is the length of the conical portion

Then,

Length of the cone (h) = H â€“ r = 15.5 â€“ 3.5 = 12 cm

Now, we know that

The curved surface area of the cone (S1) = Ï€rL, where L is the slant height of the cone.

L2 = r2 + h2

L2 = 3.52 + 122

L2 = 12.25 + 144 = 156.25

L = 12.5

So,

S1 = Ï€ (3.5)(12.5)

S1 = 137.5 cm2

Next, the curved surface area of the hemisphere (S2) = 2Ï€r2

S2 = 2Ï€ (3.5)2

S2 = 77 cm2

Therefore,

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

S = S1 + S2

S = 137.5 + 77

S = 214.5 cm2

Hence, the total surface area of the childrenâ€™s toy is 214.5 cm2