Question

The perimeter of a rectangle is 200cm. The ratio of its sides is 3:5. Find its length and breadth.

Answer 1

perimeter = l*b
                  =2(l+B)
                   =2l+2b
                  =l=5x
                   b=3x
                    2l=10x
                    2b=6x
                    16x=200cm
x=200/16 = 12.5
l=12.5*5 = 62.5
b=12.5*3=37.5

Answer 2

Perimeter = 200 cm
Let the length of rectangle be 3x and breadth be 5x
But, 
Perimeter = 2 (l + b)
200  = 2(3x + 5x)
200 = 2(8x)
16x = 200
x = 200/16 = 12.5
Length = 3x = 3(12.5) = 37.5
Breadth = 5x = 5(12.5) = 62.5