# Math Help - Trapezoid Formula

1. ## Trapezoid Formula

Hello,

OK, so I understand the basic formula to work out area of a Trapezoid

A=(b+B)/2 *H

I understand that b is the base width and B is the top width and H being height.

I need to work out the area for a Trapezoid that has been rotated 90 degrees, with in a river cross section.

So can I apply this formula to the height of either side of the section of river which would be b and B in the formula and H which now would be the width ?

Thanks for any help in advance

2. $\displaystyle b$ and $\displaystyle B$ are the parallel sides, and $\displaystyle H$ is the perpendicular distance between them.