Blue And Red Socks
Riddle: I have 10 red socks and 10 blue socks in a drawer. How many socks must I take out to ensure that I have at least one matching pair? One how many to ensure I have at least a pair of red and a pair of blue?
Answer: Three for one pair, and twelve to ensure one pair of each color.
Source: https://www.riddles.com/711
