Recall the formula for the probability of compound events. Then find the probability of each event by dividing the number of favorable outcomes by the total number of possible outcomes.
7/10, or 0.7
Practice makes perfect
We are performing an experiment to determine how well plants grow under different light sources. Out of 30 plants in the experiment, 12 receive visible light, 15 receive ultraviolet light, and 6 receive both visible and ultraviolet light. We want to find the probability that the plant receives visible or ultraviolet light. Recall the formula for probability of compound events.
P(AorB)=P(A)+P(B)-P(AandB)
We can mark the event of receiving visible light as A and the event of receiving ultraviolet light as B. To calculate the needed probabilities we need to divide the number of favorable outcomes for every event by the total number of possible outcomes, 30. Recall that 12 plants received visible light, 15 received ultraviolet light, and 6 received both.
Event
Favorable Outcomes
Probability
A
B
A and B
12
15
6
12/30
15/30
6/30
Now we can substitute the obtained probabilities into the formula for the probability of compound events and find the value of P(AorB). Let's do it!
