Parallelogram A=bh

Rectangle A=bh (lw)

Square A=bh (s²)

Trapezoid A=1/2 h(b₁+b₂) 

Triangle A=1/2 bh

PERIMETER - Add up all the sides

To find the area of shaded regions 1) find the area of the entire region 2) find the area of the unshaded part(s), 3) Subtract the area of the unshaded part from the area of the entire region

You can divide regions into smaller regions. Find the area of each smaller region. Add the areas to get the total area.