Q.If the radius of a right circular cone is \(\cfrac{r}{2}\) units and the slant height is \(2l\) units, then the total surface area is – (a) \(2πr (l+r)\) square units (b) \(πr\left(l+\cfrac{r}{4}\right)\) square units (c) \(πr(l+r)\) square units (d) \(2πr l\) square units
Answer: B
The total surface area = \(\pi \cfrac{r}{2}\left(\cfrac{r}{2} + 2l\right)\) square units
= \(\pi r\left(\cfrac{r}{4} + l\right)\) square units.
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