Question 23

Find the total surface area (in $$cm^{2}$$) of a right circular cone of diameter 21 cm and slant height 11 cm.

Solution

Radius of cone, $$r=\frac{21}{2}=10.5$$ cm and slant height, $$l=11$$ cm

Total surface area of cone = $$\pi r(l+r)$$

= $$\frac{22}{7}\times10.5\times(10.5+11)$$

= $$33\times21.5=709.5$$ $$cm^2$$

=> Ans - (D)

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