Answer: The expected value of this game is 2/3
Step-by-step explanation:
Give that
If it's black, you lose a point. If it's red, you gain a point.
And then you can stop at any time. But you should never stop when you are losing because that can guarantee 0 by drawing all the cards.
Assuming you should stop after three cards when you are +2.
The only question is whether to draw if you are +1 on the first draw.
If you draw red first, You have 1/3 chance of drawing red again and this will give you +2 points
1/3 chance of drawing two blacks and earn zero point, chance of drawing black-red and earn +1. This gives +1, so it doesn't matter whether you draw or not.
From the beginning, If you draw red (probability 1/2 you end +1. If you draw black and then draw two reds (probability 1/6 you end +1) Otherwise you break even with probability 1/3. Overall, the value is 2/3
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