Problem Solutions

Problem 1 - irrelevant information

There were no unlisted numbers because they all came from the phone book.

Problem 2 - mental set

The formula for your solution is B-A-2C. But problems 7 and 8 can be solved in fewer steps A+C. Luchins (1942) found that most people in his experiment stuck with the more cumbersome strategy that they had used in problems 1-6 and many of them couldn't solve the last 2 problems in the specified time because they kept trying to use the proven strategy.

Problem 3 - functional fixedness

Did you think of using the box that held the tacks or did you just view it as a box?

Problem 4 - unnecessary constraints

Many people place the restriction on themselves that they can't draw the line outside the square formed by the 9 dots.