1. The perimeter of base of a right circular cone is 132 cm. If the height of the cone is 72 cm, then what is the total surface area (in $$cm^2$$) of the cone?
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By: anil on 05 May 2019 02.26 am
Let radius of cone = $$r$$ cm and height = $$72$$ cm Perimeter of base = $$2pi r$$ => $$2 imesfrac{22}{7} imes r=132$$ => $$r=132 imesfrac{7}{44}$$ = $$r=3 imes7=21$$ cm Now, slant height of cone, $$l=sqrt{h^2+r^2}$$ => $$l=sqrt{(72)^2+(21)^2}$$ => $$l=sqrt{5184+441}=sqrt{5625}$$ => $$l=75$$ cm $$ herefore$$ Total surface area of the cone = $$pi r(l+r)$$ = $$(frac{22}{7} imes21)(75+21)$$ = $$66 imes96=6336$$ $$cm^2$$ => Ans - (B)
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