The ratio between the side lengths of a triangle is . If the perimeter of the triangle equals 69 cm, find the length of its longest side.
We can use the concept of "the sum of parts" to solve this problem.
Let the sides of the triangle be , , and .
The ratio of to to is . So, parts, parts, and parts.
The sum of the side lengths .
Since 23 parts , then one part .
The longest side length is 10 parts, so we can multiply the value of one part by 10 to find its length: .