Candidates’ attempt on this question was fair.  Many of them were not able to obtain the radius of the semi-circular ends. This they could obtain by subtracting the value of the given sides from 400m to get 220m.  This means that each semi-circular end will be of length 220/2 = 110m.  Thus, πr = 110 which implies that
r = 110 x 7 = 35cm       
          22
The length of the perpendicular distance between the given sides  = 2r = 70cm.
Area of the lawn  = area of rectangular part + area of semi-circular part
                            = 90 x 70m2    +   2 x ½ x πr2  m2
                            = 6300m2        +  3848.95m2 (or  3850) m2  
= 1050m2 or 10148.95m2 if the candidate is using 22/7 or 3.142 for π.