Guys you may already know this link, but this guy has an amazing library of videos on youtube for all the solutions to the problems for OG 11th edition. He has other links as well. I'm learning Probability and Combinations thru his website. Just browse thru his site and you'd be amazed with the amount of areas he has covered. OG is only one of the areas he has done
https://khanacademy.org/gmat.jsp
https://khanacademy.org/gmat.jsp
