Answer: 6/13
Explanation:
A box contains balls numbered 3 through 15. This means that the sample space = {3 , 4 ,5 , 6 ,7, 8, 9, 10, 11, 12, 13, 14, 15,}
The total number of sample space = 13
Therefore : the probability of picking 3, 5, 9, 11, 12, 15 , will be the total number of times they appear in the sample space divided by the number of sample space.
number of times 3 appears = 1
number of times 5 appear = 1
number of times 9 appear = 1
number of times 11 appear = 1
number of times 12 appear = 1
number of times 15 appear = 1
All together , they appeared 6 times
Therefore : the probability of picking one of the numbers = 6/13