Question 797137
ans:
  given that the length(L) of rectangle is thrice width(W)
 
therefore,   L=3W

when the length is increased by 8cm and width is increased by 2 cm, then the perimeter of the rectangle is 56cm

therefore,    2[(L+8)+(W+2)]=56
              2[(3W+8)+(W+2)]=56    [since, L=3W ]
              2[4W+10]=56
              4W+10=56/2
              4W+10=28
                 4W=28-10
                 4W=18
                  W=18/4
                  W=4.5cm

by    L=3W
      L=3*4.5   [ since, W=4.5cm ]
      L=13.5cm
there fore the dimensions of the new rectangle are L=13.5cm & W=4.5cm