Here is an equilateral triangle with sides of length 1.

Let's define a unit of area, $T$, such that the triangle has area $1T$.

Here are some parallelograms whose side lengths are whole numbers.

Can you find the area, in terms of $T$, of each parallelogram?

Compare the results with the lengths of their edges.

Can you explain what you've noticed?

Can you find a similar result for trapeziums in which all four lengths are whole numbers?