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pdurrant · 06-19-2010, 01:22 PM

After the extremely hard prisoners puzzle, here's an easy classic:

I keep my socks in a drawer. Every morning I get a clean pair out of the drawer. But I'm lazy — I never bother to pair up my socks after they're washed, I just bung them in the drawer as singles, and pick out a pair each morning. I don't really mind what colour socks I wear each day (so long as they're a pair), although I do like a little bit of variety, so I have more than one colour of sock.

This morning the drawer stuck — I could just open it enough to reach in to grab a sock, but I couldn't see what colour sock I was bringing out.

In the drawer (as I later worked out) were 10 black socks, 8 blue socks, and 5 brown socks (one got eaten by the laundry).

My bad luck didn't end with the stuck drawer. It took me the maximum number of goes it could have done to end up with a pair of socks

How many socks did I have to take out to end up with one pair, given that I was unlucky in the socks I pulled out?

Answers in spoiler tags please, even for this old chestnut.

06-19-2010, 01:22 PM	#1
pdurrant The Grand Mouse 高貴的老鼠 Posts: 74,077 Karma: 315558332 Join Date: Jul 2007 Location: Norfolk, England Device: Kindle Oasis	Sock Puzzle After the extremely hard prisoners puzzle, here's an easy classic: I keep my socks in a drawer. Every morning I get a clean pair out of the drawer. But I'm lazy — I never bother to pair up my socks after they're washed, I just bung them in the drawer as singles, and pick out a pair each morning. I don't really mind what colour socks I wear each day (so long as they're a pair), although I do like a little bit of variety, so I have more than one colour of sock. This morning the drawer stuck — I could just open it enough to reach in to grab a sock, but I couldn't see what colour sock I was bringing out. In the drawer (as I later worked out) were 10 black socks, 8 blue socks, and 5 brown socks (one got eaten by the laundry). My bad luck didn't end with the stuck drawer. It took me the maximum number of goes it could have done to end up with a pair of socks How many socks did I have to take out to end up with one pair, given that I was unlucky in the socks I pulled out? Answers in spoiler tags please, even for this old chestnut. Last edited by pdurrant; 06-19-2010 at 03:08 PM. Reason: edited to make it clear I just want a pair of any colour.