Final answer:
The length of the other diagonal of the kite is 20 cm.
Step-by-step explanation:
To find the length of the other diagonal of the kite, we can use the formula for the area of a kite. The formula is A = (d1 * d2) / 2, where A is the area and d1 and d2 are the lengths of the diagonals. In this case, we are given that one diagonal is 12 cm long and the area is 120 cm². Substituting these values into the formula, we have 120 = (12 * d2) / 2. Solving for d2, we get d2 = (2 * 120) / 12 = 20 cm. Therefore, the length of the other diagonal is 20 cm.