Virtu Financial·Data Scientist·Technical Phone Screen
- You have a bag with 5 red, 5 blue, and 5 green balls. You draw one ball at a time without replacement, except green balls get returned to the bag after each draw. You keep red and blue balls. Once you're holding 3 balls, what's the probability that at least 2 of them are red? Follow-up: same setup but now there are 10 red balls instead of 5. How does that change the answer?
“The green ball return mechanic is where I got tangled.”