Surface Area???

The radius of this tent - when lying flat - will  equal 18 ft

But......when standing.....this will form the slant height of the tepee

However....we have a problem.......the slant height  of this tepee  can never be the same as the standing height [ the slant height has to be greater]

Are you sure you have your numbers correct ????

I guess they are just after the (slanted) surface area of a cone of diameter 36 ft and height 18 ft.  This is given by;

Area = pi*radius*slant height = pi*18*sqrt(18^2 + 18^2)  →  pi*sqrt(2)*18^2  ft^2

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OK.....thanks, Alan......I think yours is the correct interpretation......!!!!