Given parameters:
Length of the suitcase = 24 inches
Length of the diagonal = 30 inches
Unknown:
Length of zipper required to cover the perimeter = ?
The length of this zipper is the same as the perimeter of the rectangular suitcase.
Perimeter of a rectangle = 2(L + B)
where L is the length and B is the breadth
Now, let us find the find the unknown breadth;
Using Pythagoras theorem;
30² = 24² + Breadth²
Breadth² = 30² - 24² = 324
Breadth = √324 = 18 inches
Perimeter of the suitcase = 2(24 + 18) = 84 inches.
The length of zipper that will cover this suitcase is 84inches.