Perimeter of the rectangle = 2 (L+B)
as per question 2 (L+B) = 100
L+B = 50
Area of the rectangle = L X B
we need to find the area of the rectangle so the maximum values of L and B must be 25, 25+25 =50
so The maximum value is 25 X 25 = 625
(Or)
L + B = 50
B = 50 - L
Area = A = L X B
A = L X (50 - L)
= 50 L - L^2
First derivative W.R.T 'L' gives
dA/dL = 50 - 2L
the value will be max when dA/dL will be minimum (or) zero
0 = 50-2L
L= 25
then B = 50 -L => B = 25