Question 410977
hiee there..
firstly..
we know that in a rectangle , the opposite sides are equal......................
we also know that area of a rectangle is (length) x (breadth)
so if we find the breadth then we can easily compute the area.
................................................................................
perimeter of any figure is the sum of the lenghts of all sides..
therefore,
perimeter of a rectangle = lenghth + length +breadth + breadth
                         = 2(length + breadth)
                         = 2( 21 + breadth)         
................................................................................ 
but perimeter of the rectangle is 90  cm
      therefore,
                   90    = 2(21+breadth)
      therefore, if we divide by 2 throughout, we get,
                90/2     = 2/2( 21+ breadth)
      therefore, 
                    45   = 21 + breadth
therefore,      breadth  = 45-21              (subtracting 21 from both sides)
                breadth  =  24 cm.
...................................................................
area of the rectangle    = length x breadth
                         = 21 x 24
                         = 504 sq. cm.

ans.. the area of the rectangle is 504 sq.cm.