Question 23

The curved surface area and the slant height of a right circular cone are 99 cm2 and 9 cm respectively. Find its diameter (in cm).

Solution

Let radius of cone = $$r$$ cm and slant height of cone = $$l=9$$ cm

Curved surface area of cone = $$\pi rl$$

=> $$\frac{22}{7}\times r\times9=99$$

=> $$r=\frac{99}{9}\times\frac{7}{22}$$

=> $$r=\frac{7}{2}=3.5$$ cm

$$\therefore$$ Diameter of cone = $$2\times3.5=7$$ cm

=> Ans - (B)

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