The height of a cone is 21cm- Find the area of the base the slant height is 28 cm-

Question

Toppr Admin · Accepted Answer

Correct option is A- -1078 cm-2-We have-h-21-cm and -l-28-cm-therefore l-2-r-2-h-2-Rightarrow r-sqrt-l-2-h-2-sqrt-28-2-21-2-7-sqrt-7- cm-We know- the base of a cone is a circle-therefore- Area of the base-pi r-2-dfrac-22-7-times -7-sqrt-7-2cm-2-1078cm-2-

The height of a cone is $$21$$cm. Find the area of the base if the slant height is $$28$$ cm.

Correct option is A. $$1078 cm^2$$.
We have,
$$h=21$$cm and $$l=28$$cm.

$$\therefore l^2=r^2+h^2$$
$$\Rightarrow r=\sqrt{l^2-h^2}=\sqrt{28^2-21^2}=7\sqrt{7} cm$$.

We know, the base of a cone is a circle.

$$\therefore$$ Area of the base$$=\pi r^2=\dfrac{22}{7}\times (7\sqrt{7})^2cm^2=1078cm^2$$.

The height of a cone is $$21$$cm. Find the area of the base if the slant height is $$28$$ cm.

Correct option is A. $$1078 cm^2$$.We have,$$h=21$$cm and $$l=28$$cm.$$\therefore l^2=r^2+h^2$$$$\Rightarrow r=\sqrt{l^2-h^2}=\sqrt{28^2-21^2}=7\sqrt{7} cm$$.We know, the base of a cone is a circle.$$\therefore$$ Area of the base$$=\pi r^2=\dfrac{22}{7}\times (7\sqrt{7})^2cm^2=1078cm^2$$.

Correct option is A. $$1078 cm^2$$.
We have,
$$h=21$$cm and $$l=28$$cm.

$$\therefore l^2=r^2+h^2$$
$$\Rightarrow r=\sqrt{l^2-h^2}=\sqrt{28^2-21^2}=7\sqrt{7} cm$$.

We know, the base of a cone is a circle.

$$\therefore$$ Area of the base$$=\pi r^2=\dfrac{22}{7}\times (7\sqrt{7})^2cm^2=1078cm^2$$.