Exercise 13.4

A metallic right circular cone 20 cm high and whose vertical angle is 60° is cut into two parts at the middle of its height by a plane parallel to its base. If the frustum so obtained is drawn into a wire of diameter 1/16 cm, find the length of the wire.

Solution: Let $A B C$ be the metallic cone, $DECB$ is the required frustum Let the two radii of the frustum be$\mathrm{DO}^{\prime}=\mathrm{r}_{2}$ and $\mathrm{BO}=\mathrm{r}_{1}$From $\triangle...

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A container, opened from the top and made up of a metal sheet, is in the form of a frustum of a cone of height 16 cm with radii of its lower and upper ends as 8 cm and 20 cm, respectively. Find the cost of the milk which can completely fill the container, at the rate of Rs. 20 per litre. Also find the cost of metal sheet used to make the container, if it costs Rs. 8 per 100 cm2.

Given, r1 = 20 cm, r2 = 8 cm and h = 16 cm \[\therefore Volume\text{ }of\text{ }the\text{ }frustum\text{ }=\text{ }\left(  \right)\times \pi \times h\left( r12+r22+r1r2 \right)\] It is given that...

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A fez, the cap used by the Turks, is shaped like the frustum of a cone (see Fig.). If its radius on the open side is 10 cm, radius at the upper base is 4 cm and its slant height is 15 cm, find the area of material used for making it.

  Given, For the lower roundabout end, span $(r_1)$ = 10 cm For the upper roundabout end, span $(r_2)$ = 4 cm Inclination tallness (l) of frustum = 15 cm Presently, The space of material to be...

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