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Hi All,

I have a hopefully simple question about probability:

If I have a bag of 10 marbles where 9 are red and 1 is blue, the probability of me blindly reaching into that bag and grabbing the blue one is 10%.

However, let's say I now have 20 bags of marbles, populated exactly as above. What are my chances of grabbing a blue marble in any of the bags?

Thanks!

I have a hopefully simple question about probability:

If I have a bag of 10 marbles where 9 are red and 1 is blue, the probability of me blindly reaching into that bag and grabbing the blue one is 10%.

However, let's say I now have 20 bags of marbles, populated exactly as above. What are my chances of grabbing a blue marble in any of the bags?

Thanks!

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20 bags, 10 marbles each of which one is blue - 200 marbles of which 20 are blue - chances are 20/200 - 10%

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Start your 7-day free trialSo chance of getting all blue marbles in 20 bags is 0.1^20 or 0.0.00000000000000000001

yes

even more if you use the correct 0.9 instead 0f the incorrect 0.8

To Sum Up:

20 Bags

10 Marbles/Bag

1 Blue Marble/Bag

If I reach in to each of the 20 bags, my chance of coming up with at least 1 blue marble is 87.8%.

Sound right?

But they are not separate events. The combined 20 draws (from different bags) is ONE defined event as defined by the author of this question..

That can easily be seen by looking at the first two draws. On the first draw you have a 10% chance of getting a blue ball. On the second draw you have an additional 10% chance. Clearly two 10% chances give you a better than 10% chance of getting a blue ball.

Oh, and he didn't waste my time asking if it was a homework assignment first.

This will be my last post or my last time ever reviewing this question.

Math / Science

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