Medium · Stochastic Processes & Markov Chains · Numerical · ~8 min · #80
Paint the Second Ball
Real interview · Jump Trading
A bag holds 2 red and 2 black balls. Each step, you draw two balls at random, in order, repaint the second to match the first, and return both.
What is the expected number of steps until all four balls have the same colour?
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Worked solution
Give the problem an honest attempt first, then reveal the full explanation.
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Quant TraderQuant Researcher