Area of a parallelogram
If you can find the area of a rectangle, you can quickly work out how to find the area of a parallelogram.
A parallelogram is essentially a squashed rectangle - imagine taking a rectangle and "pulling" on of the corners so the whole thing slants. You've not actually changed the area of the shape.
So the area of a parallelogram is calculated in exactly the same way as the area of a rectangle. Watch my video demonstrating this if you want to really convince yourself!
We tend to use base and height instead of length and width when working with parallelograms - this doesn't change the method though!
You must take care to always use two measurements that are perpendicular (at right angles) to each other. It's a really common mistake to accidentally use the slanted height instead.