In the dark, you are drawing socks from a drawer, one at a time (your family is asleep and you don't want to wake them...). The drawer contains 12 red socks, 11 white socks, 10 black socks, and 9 blue socks. What is the minimum number of socks you must draw from the drawer to be absolutely sure you have all of at least one of the colors?0
If I understand the question, you want to make sure you take out all the socks of at least one colour??
If you take out 38 socks you could have 11 red, 10 white, 9 black and 8 blue - each colour is one short of being a full set.
If you now take one more sock, you're guaranteed that you'll have at least one full set of all of the colours, so the answer is 39.