How can this be 1

The red triangle occupies more space on the top diagram and not as much on the bottom due to the placement, which gives me room for the other shapes. I am sure if you work out the areas etc you will figure it out..

they're just slid out sideways- the yellow piece has been moved out to the left; and then the red and darker green have been flipped/changed places w/ each other.
Not too difficult?

If you count 5 blocks in from the left edge (@ the edge of blue and yellow border on the lower) the lower top edge is exactly two blocks high, the same position on the upper top edge is just below two blocks high, so one of these is not a true triangle and by sight the upper trianle has a bit of concave on the upper edge.....so it looks like the red triangles are slighly different...wow, good illusion!

How the heck r u Capman? I read about your bike accident... did you get hurt bad?

Capman- you're such a friggin TEASE!! What's the deal w/ this damn thing? I wasn't thinking past the obvious.... apparently there's added added square here, the hole, but it's still taking up the same amount of space with all pieces seemingly being the same size as the top version... I don't see how it's an optical illusion like stardance is saying.

CapGirl....easiest way to see it is put a ruler on the top edge of both triangles...taking care to be very careful to keep the left and right corners barely touching the ruler...you will see top triagle is slightly concave...bottom triangle is slight convex. spread out over 13 blocks, you only need a minute difference to make up the area of an extra block...you see?

LOL CGWL...that's true....schoene probably knows since she's been packing lots of triangles.

There are formulas that would tell you if it is a true triangle...but you would still need to measure two sides to determine what the third side should measure and what the correct angles should be which would require some pretty special tools...

Capman....where you bin? I'm glad you only hurt your foot....is your bike o.k.?