math
posted by emma on .
One of your dresser drawers contains 10 black socks and 10 blue socks. Suppose it is dark and you canâ€™t tell what color a sock is when you look at it. If you start taking socks randomly one at a time from the drawer, how many would you have to take to guarantee that you get a pair of blue socks?
2
20
10
3
12

clearly you would have to draw 12, in case the first 10 were all black.