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

A rectangle is a rectangle whose opposite sides are parallel and equal in pairs. The side of the rectangle that is longer is called the length and is denoted by the Latin letter a, and the side that is shorter is called the width and is denoted by the Latin letter b.

By condition, the width of the rectangle is 5/9 of its length, that is:

b = 5/9 * a.

And also, the width is 15 cm, then:

5/9 * a = 15.

Let’s solve the resulting linear equation with one variable:

(5 * a) / 9 = 15;

a = (9 * 15) / 5 (proportional);

a = 9 * 3 = 27 (cm).

Answer: a = 27 cm.