Question 41976
{{{drawing(400,400,-5,75,-25,75,
line(0,0,50,0),
line(50,0,50,25),
line(50,25,0,25),
line(0,25,0,0),
line(-3,-3,53,-3),
line(53,-3,53,28),
line(53,28,-3,28),
line(-3,28,-3,-3),
locate(0,0,A),
locate(50,0,B),
locate(50,25,C),
locate(0,25,D),
locate(-3,-3,E),
locate(53,-3,F),
locate(53,28,G),
locate(-3,28,H)
)
}}}


Rectangle ABCD represents the swimming pool.
Rectangle EFGH represents the swimming pool surrounded by the concrete border.
AB = CD = 50 m and BC = DA = 25 m
EF = GH = 50 + 2x3 = 56 m and FG = HF = 25 + 2x3 = 31 m


So, perimeter of outer rectangle i.e. rectangle EFGH = 2(EF + FG) = 2(56 + 31) = 174 m.


Area of the outer rectangle = 56 x 31 = 1736 {{{m^2}}}.
Area of the inner rectangle = 50 x 25 = 1250 {{{m^2}}}.
So, area of the concrete border = 1736 - 1250 = 486 {{{m^2}}}.