The rhomboid

The area of the romboide is: $$A=a \cdot h$$

Its perimeter is: $$P=2 \cdot (a+b)$$

Calculate the area of a rhomboid with $a=5 \ cm$ and of height $3 \ cm$

$$A=3 \ cm \cdot 5 \ cm=15 \ cm^2$$

And so, the area of the romboide is: $15 \ cm^2$.