The lengths 18 cm, 24 cm and 30 cm form the sides of a right-angled triangle.
182+242=324+576=900=302
Since the squares of 18 and 24 add up to the square of 30, the numbers 18, 24 and 30 form a Pythagorean triplet, and hence, can be used to represent the three sides of a right- angled triangle.