Survo puzzles: www.survo.fi/puzzles --------------------------------------- Copyright (c) Survo Systems 2006-2012 The easiest way to solve these three problems may be using a Java Applet http://www.survo.fi/swap/puzzles.html based on the swapping method. Survo puzzle 261/2012 (40) #443-90624 A B C D 1 * * 10 * 29 2 9 14 * * 42 3 * * * * 16 4 11 * * * 49 26 50 43 17 Survo puzzle 262/2012 (130) #442-34250 A B C D 1 10 * * * 31 2 * * * * 11 3 * * * * 42 4 * * * 12 52 41 21 46 28 Survo puzzle 263/2012 (890) #443-51118 A B C D 1 * * * * 39 2 * * * * 31 3 * * * * 49 4 * * * * 17 17 39 26 54