Question 921158
perimeter (4s)= 20 cm
  each  side  (s)= 20/4  =5 cm
     diagonal = 8 cm
        half of diagonal = 4 cm
half of other diagonal =  sqrt(5^2 -4^2)
                        = sqrt(25-16)
                         =sqrt(9)
                          = 3 cm
full length of other diagonal  = 6 cm
 area  = 0.5* diagonal 1 *diagonal 2
        = 0.5*8*6
        = 24 square centimeters