word problem

Question

how do I get this answer? Your socks drawer contains 10 pairs of white socks and 10 pairs of black socks. Suppose you are in the dark and need to get one sock at a time, without knowing which one. How many socks do you need to get until you have a pair with matching color?

Answer 1

Hi Mike,

 

If you're lucky, you'll randomly draw matching socks with your first two draws.

 

If you're unlucky, you'll pull one white sock and one black sock with your first two draws. In this case, no matter what color sock you pull on your third draw, it'll definitely match one of the two socks you already have.

 

For a guarantee at a matching pair of socks, you'll need to pull a minimum of three random socks from the drawer.