To find the probability of selecting a green or striped marble from the jar, we first need to determine the total number of favorable outcomes (green or striped marbles) and the total number of marbles.
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Total number of marbles: There are 20 marbles in total.
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Number of green marbles: There are 3 green marbles and 3 green marbles with stripes. So the total number of green marbles is:
\[ 3 \text{ (green)} + 3 \text{ (green with stripes)} = 6 \text{ green marbles} \]
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Number of striped marbles: The marbles with stripes consist of the 2 yellow with stripes and the 3 green with stripes, making a total of:
\[ 2 \text{ (yellow with stripes)} + 3 \text{ (green with stripes)} = 5 \text{ striped marbles} \]
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Total favorable outcomes (green or striped): Since the green marbles with stripes have already been counted in both the green and striped categories, we should not double count them. Therefore, we can calculate the total number of favorable outcomes as follows: \[ 3 \text{ (regular green)} + 2 \text{ (yellow with stripes)} + 3 \text{ (green with stripes)} = 8 \text{ favorable outcomes} \]
Now, the probability \( P \) of selecting a green or striped marble is the number of favorable outcomes divided by the total number of marbles:
\[ P = \frac{\text{Number of favorable outcomes}}{\text{Total number of marbles}} = \frac{8}{20} \]
- Reducing the fraction: We can simplify this fraction:
\[ \frac{8}{20} = \frac{2}{5} \]
Thus, the probability of selecting a green or striped marble is
\[ \boxed{\frac{2}{5}}. \]