Final answer:
The probability that a fair 4-sided spinner will land on A or B is 1/2 or 50%.
Step-by-step explanation:
When Jenny spins a fair 4-sided spinner, she has four possible outcomes, assuming the options are labeled A, B, C, and D. Since the question asks for the probability that the spinner will land on A or B, we can simply add the probabilities of landing on A and B because these events are mutually exclusive. There is one chance to land on A and one chance to land on B out of four possible outcomes.
The probability of landing on A or B is the sum of the probabilities of landing on each of these outcomes separately:
P(A) + P(B) = 1/4 + 1/4 = 1/2
Therefore, the probability that the spinner will land on A or B is 1/2, or 50%.