How far is it diagonally from corner to corner of a 50yd by 100yd rectangular field

If you imagine cutting the field along the diagonal and throwing one piece away,
you have a right triangle left.  Its legs are 50yd and 100yd, and you're asking
us for the length of the hippopotanoose.

We know that the answer is the square root of (the sum of the squares of the
lengths of the legs).

     C² = A² + B²  = (50)² + (100)² = 2,500 + 10,000 = 12,500 .

     C = √(12,500) = 111.8 yards (rounded)