Question 2586
 If the width of the walkway is x meters, then its area is

 pi(x + 2.5/2)^2 - pi (2.5/2)^2 = pi(x^2 + 2.5 x)

 Solve: pi(x^2 + 2.5 x) <= 5,
 or x^2 + 2.5 x - 5/pi <= 0

 use pi = 3.1416 and quadratic formula,
 two roots of  x^2 + 2.5 x - 5/pi = 0 are
  0.525963319, -3.025963319
 when x is between these two roots, x^2 + 2.5 x - 5/pi <= 0
 but x width shouldbe > 0.

 Hence,x <= 0.5259 meters... max possible value of width

 Kenny