A toy is in the form of a cone of radius $ 3.5 \mathrm{~cm} $ mounted on a hemisphere of same radius. The total height of the toy is $ 15.5 \mathrm{~cm} $. Find the total surface area of the toy.


Given:

A toy is in the form of a cone of radius \( 3.5 \mathrm{~cm} \) mounted on a hemisphere of same radius.

The total height of the toy is \( 15.5 \mathrm{~cm} \).

To do:

We have to find the total surface area of the toy.

Solution:

Radius of the cone $r = 3.5\ cm$

Total height of the toy $H= 15.5\ cm$
Height of the conical part $h = 15.5 - 3.5$

$= 12\ cm$

This implies,

Slant height of the cone $l=\sqrt{r^{2}+h^{2}}$

$=\sqrt{(3.5)^{2}+(12)^{2}}$

$=\sqrt{12.25+144}$

$=\sqrt{156.25}$

$=12.5 \mathrm{~cm}$

Therefore,

Total surface area of the toy $=$ Curved surface area of the conical part $+$ Curved surface area of the hemispherical part

$=\pi r l+2 \pi r^{2}$

$=\pi r(l+2 r)$

$=\frac{22}{7} \times 3.5(12.5+2 \times 3.5)$

$=\frac{22}{7} \times \frac{7}{2}(12.5+7)$

$=11(19.5)$

$=214.5 \mathrm{~cm}^{2}$

The total surface area of the toy is $214.5\ cm^2$.

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Updated on: 10-Oct-2022

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