Steps: 2 Marks
Application: 1 Mark
Answer: 1 Mark
The given area will be inscribed between two rectangles of length and breadth.
We can imagine as a rectangle whose length has been increased on both the sides. 
So, the sides  of the outer triangle are,
Length = 35 + 5 = 40 m
And breadth = 40 + 5 = 45 m

40m and 45m, 40m and 35m respectively.
The area of the footpath = Area of outer rectangle - Area of inner rectangle
Area of the rectangle = length$\times$breadth
$\therefore$ On substituting the values we get;

Area required = (45) $\times$ (40) - (40) $\times$ (35)

= 1800 - 1400

= 400$m^2$
The area of the footpath is 400$m^2$.