Puzzle
 

easy, the second thing is not a triangle!

edit: the first figure isnt a triangle either

2/5 is not equal to 5/8

huh?
How are they not triangles, I am confused.

And what do you mean by 2/5 is not equal to 5/8?

If you look carefully at the red triangle, you'll see that its a 8x3 triangle, while the green one is a 5x2 triangle. Their hypotenuses are not parallel.

another way to look at it:

if the top large triangle was a real triangle, it would have area 13*5/2 = 32.5.

The pieces have area 12, 8, 7, and 5. The sum of this is 32. Hence, .5 of a square's area would need to be added to this shape to make it a true triangle. This area would be along the slightly-bent hypotenuse.

In the second shape, the hypotenuse is bent outwards, occupying an extra .5. It is the difference between lacking .5 and having .5 too much that allows the empty square.

Tricky bastards

My geometry teacher should frown on me