So if you draw it, the diagonal makes a right triangle. To find the diagonal, use the pathagorean theorem. a^2+b^2=c^2 so 900 + 1600 =c^2 So solve that: 2500=c^2 so the length of c, the diagonal is 50. BE is half of BD, so you divide 50 by two.
The answer is BE = 25