OK, a triangle first of all needs to have a certain condition satisfied. The length of one side of a triangle can not equal the length of 2 sides combined. So in a triangle a + b = c, a + b can not be less than c (a + b ≮ c). Therefore, there are only a few possibilities that will work here. Let's find them:
16, 19, 43; no
16, 19, 50; no
16, 43, 50; yes
19, 43, 50; yes
Since only 2 out of 4 form triangles, there is a 50% chance you'll pick the right segments to form a triangle.
