Two identical triangles with sides 3 cm, 4 cm and 5 cm long were attached with the sides to one another

Two identical triangles with sides 3 cm, 4 cm and 5 cm long were attached with the sides to one another so that a rectangle turned out. What is the perimeter of this rectangle?

If two triangles form a rectangle, then they are 2 right triangles. In right-angled triangles, the hypotenuse is the longest side, which means the sides of 3 cm and 4 cm are legs. We calculate the perimeter of the rectangle if the legs are the sides of the rectangle:
3 + 3 + 4 + 4 = 6 + 8 = 14 cm.
Answer: the perimeter of the resulting rectangle is 14 cm.