This video includes 3 puzzles that ghosts are useful mathematically. Can you figure them out? Puzzle 1: A father left 17 goats to his three sons. His will promised 1/2 of the goats to the oldest son, 1/3 to the middle son, and 1/9 to the youngest son. But the sons could not divide 17 evenly. How did they split up the goats? Puzzle 2: You have several identical bricks and a ruler. You want to measure the diagonal of a single brick without using any formulas. How can you do it? Puzzle 3: At 6 am a monk started climbing a mountain and reached the top at 8 pm, where he slept for the night. The next morning at 6 am he descended the mountain on the same path and reached the bottom at 8 pm. A mathematician made an interesting observation: by the facts, there must be some spot on the mountain that the monk occupied at exactly the same time of day for both trips. Why is this? Blog post (with text solutions): http://mindyourdecisions.com/blog/2014/10/27/monday-puzzle-mathematicians-do-believe-in-ghosts/#.ViELPH6rRaQ If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is most convenient for you. My Blog: http://mindyourdecisions.com/blog/ Twitter: http://twitter.com/preshtalwalkar Facebook: https://www.facebook.com/pages/Mind-Your-Decisions/168446714965 Google+: https://plus.google.com/108336608566588374147/posts Pinterest: https://www.pinterest.com/preshtalwalkar/ Tumblr: http://preshtalwalkar.tumblr.com/ Instagram: https://instagram.com/preshtalwalkar/ Patreon: http://www.patreon.com/mindyourdecisions Newsletter (sent about 2 times a year): http://eepurl.com/KvS0r My Books "The Joy of Game Theory" shows how you can use math to out-think your competition. (rated 4/5 stars on 23 reviews) https://www.amazon.com/gp/product/1500497444 "The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" is a handbook that explains the many ways we are biased about decision-making and offers techniques to make smart decisions. (rated 5/5 stars on 1 review) https://www.amazon.com/gp/product/1523231467/ "Math Puzzles Volume 1" features classic brain teasers and riddles with complete solutions for problems in counting, geometry, probability, and game theory. Volume 1 is rated 4.5/5 stars on 11 reviews. https://www.amazon.com/gp/product/1517421624/ "Math Puzzles Volume 2" is a sequel book with more great problems. https://www.amazon.com/gp/product/1517531624/ "Math Puzzles Volume 3" is the third in the series. https://www.amazon.com/gp/product/1517596351/ "40 Paradoxes in Logic, Probability, and Game Theory" contains thought-provoking and counter-intuitive results. (rated 4.9/5 stars on 7 reviews) https://www.amazon.com/gp/product/1517319307/ "The Best Mental Math Tricks" teaches how you can look like a math genius by solving problems in your head (rated 4.7/5 stars on 3 reviews) https://www.amazon.com/gp/product/150779651X/ "Multiply Numbers By Drawing Lines" This book is a reference guide for my video that has over 1 million views on a geometric method to multiply numbers. (rated 5/5 stars on 1 review) https://www.amazon.com/gp/product/1500866148/