We have a randomly selected prize out of 9 objects (4 rings, 4 headsets and 1 camera).
a) We have to calculate the odds in favor of Mary winning a ring.
The odds can be expressed as the proportion (or quotient) between the probabilities of winning a ring and the probabilities of not winning a ring.
This will also be equal to the number of outcomes that will be a ring (4 elements are rings) divided by the number of outcomes that are not a ring (5 elements are not a ring):
b) Now, we have to calculate the odds against Mary winning a ring.
This will be the inverse of the previous result, as we have to divide the probability of not winning a ring by the probability of winning.
We can then write:
Answer:
a) 4 : 5
b) 5 : 4