A box has inside 3 black balls, 2 red balls and 3 green balls. If you pick a black ball you win 2 euros, if you pick a red ball you lose 1 euro, and if you pick a green ball nothing happens. You pick 100 times a ball. What is the probability to win at least 50 euro. B Can you help me to solve this one?
Can you compute your expected gain or loss for each time you pick a ball?
This is then a binomial experiment with 100 trials (which accounts for the comment suggesting approximation by a normal random variable).