126 cm^2
Lets assume sides of rectangle are a and b, then we have: (a+b)*2=48 cm --------> (1) SQRT (a^2+b^2)=18 cm --------> (2) S=ab=?
(1) ---> a+b=24 cm (2) ---> a^2+b^2=324 cm^2 (1)^2- (2) = (a+b)^2- (a^2+b^2) = 2ab = 252 ---> ab= 126 cm^2