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Question
The total surface area of a cone of radius `r/2` and length 2l, is
Options
`2 pi r (1 + r)`
` pi r (1 + r/4)`
`pi r (1+ r) `
` 2 pi rl`
Solution
The formula of the total surface area of a cone with base radius ‘r’ and slant height ‘l’ is given as
Total Surface Area = `pi r(l+r)`
Here it is given that the base radius is ‘`r/2`’ and that the slant height is ‘2l’.
Substituting these values in the above equation we have
Total Surface Area = `pi (r/2)(2l+r/2)`
= `pir(l+r/4)`
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