reinout-g: Here are the new probability puzzles!
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Easier one:
A special machine contains 100 red, 100 green and 100 blue marbles.
The machine performs the following four operations.
First, the machine randomly picks 50 marbles from the entire batch.
Secondly the machine divides the marbles into one group of 20 and one group of 30
Furthermore, the machine picks and shuffles 5 marbles of the group of 20 and 10 marbles of the group of 30.
Finally, the machine randomly chooses one of the final 15 marbles it picked and shows it to you.
Assuming you cannot see anything which happens inside the machine.
What are the odds the machine will show you a red marble?
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