To find the probability of selecting a green or striped marble from the jar, we first need to identify the total number of marbles and the number of marbles that are either green or striped.
The jar contains the following marbles:
- Red: 5
- Green: 3
- Yellow with stripes: 2
- Blue: 7
- Green with stripes: 3
Now, let's summarize the counts:
- Total green marbles: \( 3 \)
- Yellow with stripes: \( 2 \)
- Green with stripes: \( 3 \)
Next, we find the total number of striped marbles:
- Yellow with stripes: 2
- Green with stripes: 3
Thus, the total number of striped marbles is: \[ 2 + 3 = 5 \]
Now we calculate the total number of marbles that are either green or striped. Note that the "green" marbles (3) include some of the striped ones (3) already counted, so we add but do not double-count the green marbles with stripes:
\[ \text{Total green or striped} = \text{Total green} + (\text{Total striped} - \text{Green with stripes}) \] This gives us: \[ = 3 + (5 - 3) = 3 + 2 = 5 \]
So, the total number of marbles that are either green or striped is 5.
Finally, we calculate the total number of marbles in the jar, which is 20. The probability of selecting a marble that is either green or striped is given by:
\[ P(\text{green or striped}) = \frac{\text{Number of green or striped marbles}}{\text{Total number of marbles}} = \frac{5}{20} \]
To simplify the fraction: \[ \frac{5}{20} = \frac{1}{4} \]
Thus, the probability of selecting a green or striped marble is:
\[ \boxed{\frac{1}{4}} \]
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