In a rectangle the ratio of the length to the width is 5: 2, and its perimeter is 126 centimeters.

Let the length be 5x and width be 2x
Perimeter of rectangle= 2(length + bredth)
                                   = 2(5x+2x) =126
                                   ∴ 2(7x)=126
                                      14x = 126
                                          x=9
 Therefore, length = 5*9=45 
and bredth= 2*9=18