Let radius of circle = r
Perimeter of circle = 2*pi*r
Area of circle = pi*r*r
Edge of square = a
Perimeter of square = 4*a
Area of square = a*a
Edge of Triangle = x
Perimeter of Triangle = 3*x
Area of Triangle = root(3)x*x/4
Perimeter is same i.e. 2*pi*r = 4a = 3x =t
r = t/2*pi,
a = t/4
x = t/3
Area of circle, square, triangle are t*t/4*pi, t*t/16, root(3)t*t/36 = t*t (1/4*pi, 1/16, root(3)/36)
4*pi < 16 < root(3)/36
i.e. Area (circle) > Area (square) > Area (triangle)