Volume of a triangular solid with varying base areas

[pdaniels10]

I have a triangular (scalene) shaped pond with the area at the top (base1) = 8719.5 SF , side slopes of 3:1 (h:v), and area at the bottom (base 2) = 207.4SF. The pond is 10' deep. How do I calculate the volume? I've tried average end area formula (V=L*(A1+A2)/2 - gave me 44,634CF) and prismoidal formula (V = L*(A1+4Am+A2)/6 - gave me 19,706CF - I found Am to be the area at 5' deep = 2904.1SF). Are either of these correct? If not, what is the correct method?

Thanks

 

[tkhunny]

Can you find the volume of the whole structure if you extend the sides until they meet at a point?

 

[pdaniels10]

You mean like a triangular pyramid? I know how to find the volume of a triangular pyramid, is my pond similar?

 

[pappus]

I have a triangular (scalene) shaped pond with the area at the top (base1) = 8719.5 SF , side slopes of 3:1 (h:v), and area at the bottom (base 2) = 207.4SF. The pond is 10' deep. How do I calculate the volume? I've tried average end area formula (V=L*(A1+A2)/2 - gave me 44,634CF) and prismoidal formula (V = L*(A1+4Am+A2)/6 - gave me 19,706CF - I found Am to be the area at 5' deep = 2904.1SF). Are either of these correct? If not, what is the correct method?

Thanks

If I understand your question correctly your pond looks like a frustrum of a pyramid (but upside down ) Have a look here: http://en.wikipedia.org/wiki/Frustum

With your values I've got a volume of V = 34,238.9 cft.

 

[pdaniels10]

That helps a lot, thanks.