# Solution to the Triangles Formed from Rectangles Puzzles +-- {.image} [[TrianglesFormedfromRectangles.png:pic]] > The area of the yellow triangle is $15$. What’s the total orange area? =-- ## Solution by [[Crossed Trapezium]] +-- {.image} [[TrianglesFormedfromRectanglesLabelled.png:pic]] =-- In the above diagram, the line $B E$ defines two trapeziums: $A B E F$ with $A B$ parallel to $F E$, and $B C D E$ with $B C$ parallel to $E D$. In each trapezium the shaded areas are the side triangles in a [[crossed trapezium]] and therefore are of equal area. Put together, the total orange area is the same as the yellow area and so is $15$.