We have to calculate the probability that we choose a marble that has either red or green on it.
We have a total of 13 marbles.
We can draw a Venn diagram to look at the green and red marbles:
We can see in the diagram that is expected to all the marbles that have red on it to have also green, because they are not mutually exclusive.
Then, we can calculate the probabilities as:
[tex]\begin{gathered} P(G\cup R)=P(G)+P(R)-P(G\cap R) \\ P(G\cup R)=\frac{7}{13}+\frac{5}{13}-\frac{5}{13}=\frac{7}{13} \end{gathered}[/tex]
NOTE: If we write the exact color of each marble we will get:
1) 6 blue marbles
2) 2 only green marbles, as 5 of the 7 marbles that have green are "red and green" marbles.
3) 0 only red marbles: all 5 of the marbles that have red are "red and green"marbles.
4) 5 red and green marbles.
Then, if we add, we get 6 + 2 + 5 = 13 marbles.
The marbles that have red or green are: 2 green and 5 red and green, so there are 7 marbles that have red or green.
Then, the probability is equal to number of successful events / total events = 7/13.
It is the same result as the previous calculation.
Answer: the probability is 7/13.
