SOLUTION: Find the total area of the frustum of a regular square pyramid which is inscribed in the frustum of a cone whose upper and lower base diameters are 11 ft and 15 ft respectively,

Algebra ->  Bodies-in-space -> SOLUTION: Find the total area of the frustum of a regular square pyramid which is inscribed in the frustum of a cone whose upper and lower base diameters are 11 ft and 15 ft respectively,       Log On


   



Question 1194401: Find the total area of the frustum of a regular square pyramid which is inscribed
in the frustum of a cone whose upper and lower base diameters are 11 ft and 15 ft
respectively, and whose altitude is 19 ft.

Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find the total area of the frustum of a regular square pyramid which is inscribed
in the frustum of a cone whose upper and lower base diameters are 11 ft and 15 ft
respectively, and whose altitude is 19 ft.
~~~~~~~~~~~~~~~

Use the formula for the volume of a regular pyramidal frustum

    V = %281%2F3%29%2Ah%2A%28A%5B1%5D%2BA%5B2%5D%2Bsqrt%28A%5B1%5D%2AA%5B2%5D%29%29,


where h is the height,  A%5B1%5D  and  A%5B2%5D  are the base areas

(see this source https://mathworld.wolfram.com/PyramidalFrustum.html) .


In your case, the bases are the squares with their diagonals 11 ft and 15 ft.


Their areas are  11%5E2%2F2 square feet  and  15%5E2%2F2 square feet, respectively;
h = 19 ft.  Therefore, the volume of the frustum is


    V =  = %281%2F3%29%2A19%2A%28121%2F2+%2B+225%2F2+%2B+%2811%2A15%29%2F2%29 = 

      = %281%2F3%29%2A19%2A%28%28121%2B225%2B165%29%2F2%29 = %281%2F3%29%2A19%2A%28511%2F2%29 = 9709%2F6 = 1618.167  cubic feet  (rounded).


ANSWER.  The volume is  9709%2F6 = 1618.167  cubic feet  (rounded).

Solved.