The width of the rectangle is 15 cm, which is 5/9 of its length, find the length of the rectangle.

The width of the rectangle is 15 cm, which is 5/9 of its length, you need to find the length of the rectangle;

To do this, we make up the proportion:

The equality of two relations is called proportion;

The product of the extreme terms of the proportion is equal to the product of its middle terms;

To find the unknown extreme term of the proportion, you need to divide the product of the middle terms of the proportion by the known extreme term;

The length is unknown, let us designate “x”;

15 cm is 5/9 part;

x cm is 9/9;

15 x 9/9 = x x 5/9;

15 × 1 = 5 / 9x;

15 = 5 / 9x;

x = 15: 5/9;

x = 15 × 9/5;

We shorten:

x = 3 × 9;

x = 27;

Answer: the length of the rectangle is 27 cm.