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Riddles and Puzzles

Riddles and puzzles can help exercise the creative parts of your mind.

Riddles are puzzles that are usually based on partial, vague, or mis-interpretable information. Riddles are also usually intentionally ill-structured. Puzzles are questions intended to be solved by non-conventional means. Being able to solve riddles and puzzles is a good indicator that you can think laterally; in other words, that you are a creative problem solver.

Design problems are also usually ill-structured and full of partial and vaguely stated information. Only design problems are not intentionally so.

If riddles and design problems share so many characteristics, then maybe they share solution methods too. So learning to solve riddles can help you think more clearly about design problems. Solving riddles won't make you a great designer, but it'll help you learn to think.

So try these riddles & puzzles.

The nut and the tube

Say you have a peanut at the bottom of a tall, narrow glass tube. How do you get it out?

Watch the first 30 seconds of this video, then pause it. Consider: how would you solve the problem? Once you have an answer, or you give up, watch the rest of the video.

What's the lesson there?

The 1st Grader Parking Puzzle

According to this source, a question posted on Sina Weibo is part of an entrance exam for 1st grade elementary school children in Hong Kong.

Per the test, you have 20 seconds to look at the figure below and answer the question “What is the number of the parking spot where there car is?”

parkingpuzzle.jpgFig. 1: The Parking Spot Puzzle

6 or 9?

6or9mathpuzzle.jpgFig. 2: Is the result 6 or 9?

Helium Balloons in Cars

Say you go for a drive with a helium-filled balloon. In what direction do you think will happen to the balloon will move when you:

  • accelerate?
  • decelerate?
  • turn right?
  • turn left?

Once you're sure about your answers, consider this video:

Child's Play

A child can usually solve this puzzle faster than an educated adult.

Consider the following sequence. What number replaces the ???? on the last line?

  • 8809 = 6
  • 7111 = 0
  • 2172 = 0
  • 6666 = 4
  • 1111 = 0
  • 3213 = 0
  • 7662 = 2
  • 9312 = 1
  • 0000 = 4
  • 2222 = 0
  • 3333 = 0
  • 5555 = 0
  • 8193 = 3
  • 8096 = 5
  • 7777 = 0
  • 9999 = 4
  • 7756 = 1
  • 6855 = 3
  • 9881 = 5
  • 5531 = 0
  • 2581 = ????

Square, Triangle, Circle

Consider three holes in a flat plate. The first is square, 2 inches on a side. The second is an equilateral triangle, 2 inches on a side. The third is a circle 2 inches in diameter. What is the cross-sectional shape of a rod that will (a) pass through each of the holes and (b) minimise the amount of space between the rod and any of the holes?

What a Yoke!

Create a low-cost, lightweight container that will prevent an egg from breaking when dropped from a 30 ft height onto concrete.

Check, mate

Two people play three games of chess. Each player wins two games. There are no draws. How is this possible?

Nine Dots, Four Lines

Fig. 3: A classic puzzle.

The figure to the right shows nine dots in a grid. Connect the dots with only four straight lines without lifting your pen off the page.

The Einstein Riddle

Allegedly, Albert Einstein created this riddle, and claimed only 2% of the world's population could solve it. Rumour has it that President J.F. Kennedy solved it in 21 minutes. It took me three days. Here it is.

There are 16 facts available; this is all you need to solve the riddle. The facts are:

  1. There are five houses.
  2. The Englishman lives in the red house.
  3. The Spaniard has a dog.
  4. Coffee is drunk in the green house.
  5. The Ukrainian drinks tea.
  6. The green house is immediately to the right of the ivory house.
  7. The Old Gold smoker owns snails.
  8. Kools are smoked in the yellow house.
  9. Milk is drunk in the middle house.
  10. The Norwegian lives in the first house.
  11. The Chesterfield smoker lives next door to the man with the fox.
  12. Kools are smoked in the house next to the house with the horse.
  13. The Lucky Strike smoker drinks orange juice.
  14. The Japanese smokes Parliaments.
  15. The Norwegian lives next door to the blue house.
  16. In each house there is one nationality, one pet, one brand of cigarette, and one liquid drink1).

There are two questions to answer:

  1. Who drinks water?
  2. Who owns the zebra?

The einstein riddle solution (only accessible to instructors).

The Fly and the Trains

Two trains are 100 km apart travelling toward each other on the same track. Each train travels at 50 kph. A fly leaves the first train heading toward the second train the instant they are 100 km apart. The fly travels at 60 kph (relative to the ground). When the fly reaches the second train, it turns and heads back to the first train at 60 kph. When the fly reaches the first train, he turns again. This process continues until the two trains collide.

How far does the fly travel until it is crushed?

The fly and the trains solution (only accessible to instructors).

Train stability

What keeps a train on its tracks? How does that work exactly?

Please don't peek at this solution till you've honestly tried to work it out.

I guess this tells you how old this riddle is. I mean, when was the last time you saw cigarettes mentioned so prominently.
design/puzzles_and_riddles.txt · Last modified: 2020.03.12 13:30 (external edit)