What is the formula for finding the volume of a trapezium?

[defenderprc]

Volume of a trapezium = height * (top area +botton area)/2

 

[HallsofIvy]

Assuming that by "trapezium" you mean "a three dimensional figure having parallel top and bottom and planar sides", yes. Basically, '(top area+ bottom area)/2' is the "average" base area. As long as you have linear formulas (and since you have planar sides, this is linear) you can calculate an average like that.