Vera has 10 white socks, 10 black socks, 10 brown socks, 10 blue socks, and 10 red socks. How many socks (at a minimum) must she pull out of her sock drawer to ensure at least two matching pairs of different colors?
Well, she could pull out 10 white then 1 black, 1brown 1 red, 1 blue. And then the next draw would complete the second pair.
So I get 15.