In a rectangle with sides 18 cm and 8 cm long, a diagonal is drawn. Determine the area of the triangles.

Let’s find the area of a rectangle, the lengths of the sides of which are known by the problem statement:
S = a * b = 18 * 8 = 144 (cm²).
In this rectangle, one diagonal was drawn, thereby forming two equal right-angled triangles (the legs are equal, the hypotenuse, it is the diagonal, is common). Let’s find the area of the formed triangles:
144/2 = 72 (cm²).
Answer: the area of the triangles is 72 cm².