We can eliminate choice 50%, since BD splits the square in half, but the shaded doesn't fill it up.
So our answer is less than 50. We remove the right traingle at the bottom which has an area of 4*1/2 = 2. 2/16 = 1/8
That's another 12.5%.
Oops we missed the small one! We over counted that one.
First, 50-12.5 = 37.5, but we need to add that, and the size appears to be 2.5%, since it's a similar triangle of the shaded, but like 16 times smaller
also to clarify, the small triangle is probably 2.5% since it's probably no more than a third of the right triangle there, but if it's even 1 third, it would be 4 percent and STILL around 40.
I'm very sure it's 40 but it's more of a gut feeling than hard proof.
+1005 