Lateral thinking

Lateral thinking means thinking correctly about a problem, even if you have to temporarily ignore rote learning and misconceptions. For example :
It took two hours for two men to dig a hole five feet deep. How deep would it have been if ten men had dug the hole for two hours ?

Simplistically, the answer appears to be 25 feet deep. This is based on a few incorrect assumptions :
  • The plan is to make the hole deeper, rather than longer or wider, as with a ditch.
  • Ten men have just as much room to move around and shovel in (without getting in the way of other men) as two men do.
  • Each of the ten men will work just as hard as the two men will—generally, the more people you have working on a project, the more each person will assume he can slack off.

The correct answer—whatever it is—goes against standard mathematical training. This does not make it incorrect; standard mathematical training does not teach how to apply math to the real world very well, except with finances. Lateral thinking gets answers that are correct (or closer to the truth) because it takes into account more factors and the meanings of the words.

Example problems

  • How long would it take to dig half a hole ?
    • You can't dig half a hole.

  • If one egg takes three minutes to boil, how long do two eggs cook ?
    • About three minutes (more energy is needed to boil the water than the eggs).

  • If a knot in a 5-foot rope takes five minutes to undo, how long would a knot in a 10-foot rope take to undo ?
    • Also five minutes (the length of rope usually has nothing to do with the complexity of the knot).

Further reading

  • Edward De Bono, Lateral Thinking : Creativity Step by Step, Harper & Row, 1973, trade paperback, 300 pages, ISBN 0060903252

copyright 2004