Khan Academy: "Brain Teasers"

Pick out a few videos to watch on brain teasers. The puzzle will be introduced to you at the beginning of the video. You should pause the video and attempt to solve the puzzle before viewing the solution. Watch the solutions only if you absolutely cannot solve the puzzle; then, go back and reattempt the problem.

Click http://www.khanacademy.org/math/brain-teasers link to open resource.