TeUpon examination of the dissection of the trapezoid on each side, we can see that we can make out two isosceles triangles on each side. The angle on the corners of the base can be determined by sine function. we can also use pythagorean theorem, in which the other length is equal to 3". This leaves the shorter base equal to 11-2*3 equal to 5"
The answer is 1/2. I think that since the question is about Box B , only boxes will be taken into consideration. Since the total number of boxes are two and box b is one ,the probability of the box being B is 1/2.
