Classical don't think too much, calculate exercise. 1. Probability to pick green after a red for a given n is p = (100-n)/99 2. For all possible n given the f

Classical don't think too much, calculate exercise. 1. Probability to pick green after a red for a given n is p = (100-n)/99 2. For all possible n given the first ball was red -> Integral_[0..100] (100-n)/99 * p(n|red) dn 3. So you need p(n|red) which is obviously different from p(n) for instance n=0 is not possible anymore -> p(n=0) = 1/101 != p(n=0|red) = 0 4. Again don't think to much, calc ... p(n|red) = p(red|n)p(n)/p(red) p(n) = 1/101 (1 of 101 possible n, constant due to uniform distribution), p(red)=0.5 (due to symmetry since p(n) is uniform), p(red|n) = n/100 (n of 100 balls are red) -> p(n|red) = n/5050 5. plausibility check -> sum of p(n|red) for all n should be 1 -> (0 + 1 + 2 .. 100) / 5050 = 5050/5050 = 1 6. Hardest part, the integral from step 2. -> wolfram alpha says 0.33 7. It's a don't-think-too-much-calculate result, so don't be too confident )))