I don't get it.

eer looks like the pic has gone. Must be a trick of the www.

Try this.....

Hmmm, good question. They should have the same area.
Colour me confused.

Ahh I see - The Red and Green triangles aren't infact SIMILAR. If they were, the Green triangle would be 1.875 units high (not 2 units).
Thus, the overall "big triangle" isn't in-fact a triangle at all (it has a kink in the hypotenuse).

Overall area of figure 1 is:
Going by the indivdual shapes - Total Area is:
12 sq units + 5 sq units + 15 sq units = 32 sq units
Going by the (false) area of the (false) BIG Triangle:
1/2bh = 0.5*13*5 = 32.5 sq units.
A difference of 0.5 sq units.

Rearranging figure 1 introduces this difference again (2*0.5 sq units) - meaning that we get 1 sq unit left over.

Good puzzle tho.

Jas

Overall area of the (false) big triangle in figure 1 is:

You've lost me in the maths, but I can see the trick. The individual pieces are the same in each picture, but Figure 1 has a kink in the hypotenuse inwards and Fig. 2 has a kink outwards.