I have a drawer full of socks. There are 10 socks of each colour, red, green, brown and grey, evenly mixed. In the morning, when it is very dark, I need to pull out a pair of socks of the same colour. How many must I pull out of the drawer to ensure that I have at least one pair of matching socks?



5 socks.

the first 4 may be different colors.the fifth will match any of the color.