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View Full Version : What's the formula for a Trapezoid's volume?



anthropas
02-02-2004, 05:01 PM
Hi all,

I can't remember how to figure the volume of a Trapezoid. Can anyone remind me of the formula or point me to a link of it on the web. I searched for a while, but couldn't find one.

Thanks,

Anthropas

helotaxi
02-02-2004, 05:46 PM
A trapezoid is 2D and does not have volume, only area. If you mean the area then the formula is (L1+L2)/2 * H.

anthropas
02-02-2004, 08:26 PM
Ok, let me try this again. You all know the shape most pre-fab single sub boxes come in? Where the back of the box is slanted and the base is bigger than the top. Almost like a crooked pyramid that has a flat top. I thought that was considered a trapezoid, but was corrected. Anyway, I would love to know the formula for figuring out its volume if anyone can understand what I just described

Anthropas

Omarvelous
02-02-2004, 08:32 PM
Like a Wedge Enclosure? What you could do is divide it up into a rectangle and triangle. Triangle is 1/3BH and Rectangle is LWH. Add them together, and you get your total volume.

helotaxi
02-02-2004, 09:41 PM
Another method is to add the depth of the top to the depth of the bottom, divide that by two and multiply by the height ( find the area of the trapezoid that makes one end of the box in other words) and multiply by the width of the enclosure. To figure air volume, correct the outer dimensions for the thickness of the material.

helotaxi
02-02-2004, 09:45 PM
Like a Wedge Enclosure? What you could do is divide it up into a rectangle and triangle. Triangle is 1/2BH and Rectangle is LWH. Add them together, and you get your total volume.
Fixed your formula above in red for the area of the triangle, but you still have to multiply by the length of the enclosure to get volume, which you can add to the volume of the rectangle part. If the enclosure has two angled sides you must do each triangle portion individually or just use the equation I gave in my previous post.

sumone
02-02-2004, 11:41 PM
find area of one side (the trapezoid) with helotaxi's formula - ((a+b)/2)*h where a and b are the parallel sides and h is the distance between them. Multiply that by the distance between the two sides (aka the two trapezoids)