Area of the rectangular field = 54 x 35 = 1890m2.
Let the width of the path be x m. The path is shown in the following diagram:

Length of the park excluding the path = (54 - 2x)m
Breadth of the park excluding the path = (35 - 2x)m
Thus, we have:
Area of the path = 420 m2

The width of the path cannot be more than the breath of the rectangular field.
∴ x = 2.5 m
Thus, the path is 2.5 m wide.