The water jar problem (Luchins, 1942)

(Start with problem #1 and see if you can solve all 9)

 How would you use 3 jars with the indicated capacities to measure out the desired amount of water? Problem # Jar A Jar B Jar C Desired Quarts of water 1 29 3 . 20 2 21 127 3 100 3 14 163 25 99 4 18 43 10 5 5 9 42 6 21 6 20 59 4 31 7 23 49 3 20 8 15 39 3 18 9 28 76 3 25

Were you able to solve all 9? See the discussion below once you have given it a try.

• Set can prevent you from choosing a good solution strategy
• "Persistence of set" in the water jar problem (Luchins, 1942)
• Problems 2 thru 6 can all be solved by filling Jar B, then subtracting Jar A once, then subtracting Jar C twice. This creates a "set" for solving the problems this way.
• Problems 7 and 8 can be solved using the same method as the previous problems, but they could be solved more efficiently by starting with Jar A instead. The "set" for starting with Jar B often prevents people from seeing the simpler solutions.
• Problem 9 can not be solved in the same way as problems 2 thru 6. You must break out of the set to find a solution.