Permutation and combination of distinct Rings vs distinct balls

Question

Sir/Mam, I had read a question that goes as follows-"In how many ways can 4 rings be worn in index, ring and middle finger if there is no restriction of the number of rings to be worn on any finger? " The answer was -" each of the 4 rings could be worn in three ways, hence answer is 3 * 3 * 3 * 3 =3^4 ways". Now the second question is " five balls of different colours are to be placed in three different boxes such that any box contains at least 1 ball. What is the maximum number of different ways in which this can be done ? " And the answer was 150. Now why can't I interpret the second question as " each of the five different balls can choose any of the three boxes" and give an answer as 3 * 3 * 3 * 3 * 3 =3^5 ? Please explain this in detail with simple terms , so that a student like me who is weak in mathematics can understand this... Thank you