Monthly Archives: September 2016

On the isle of Odders and Eveners (1)

Which day of the week is it?**/*****
Inspector Simon Mart opened his eyes. The lights hurt and he quickly closed them again. Slowly his memories returned. He had landed on the island of Odders and Eveners in the Logico archipelago. Like all islands in this archipelago, the inhabitants had strange habits when it came to speaking the truth and when lying.
The Odders spoke the truth on the odd days of the week: On Sunday, Tuesday, Thursday, and Saturday, and lied on the other days.
The Eveners spoke the truth on the even days of the week, on Monday, Wednesday, and Friday, and lied on the other days.
On the evening of his arrival, he had taken part in the arrest of some smugglers, and he had been beaten unconscious with a coconut. How long would he have been unconscious?

A nurse entered the room of the hospital and he heard a sweet voice asking how he felt. He quickly opened his eyes and saw that it was an indigenous inhabitant of the island.
“What day is it?” he asked.
“Tomorrow I will speak the truth,” she answered cryptically, in the same reassuring tone that some mothers use against their toddlers. Just before he lost conscious again, he realized that the nurse had actually answered his question.

What day of the week was it?

You can check your solutions here

Sliding coins puzzles

There are many beautiful puzzles with coins. I don’t mean those which have to do with the value of the coins, but with the puzzles in which you have to move coins around. Neither do I want to discuss the puzzles which are about arranging coins in a straight line. These are often represented as planting trees in a row, and I discussed them here.

While on holiday in France this summer, I bought two puzzle booklets in the ‘aires’, the road stops with a restaurant, a gasoline station, a toilet and some more. One of them, ‘Best of jeux de vacances, 700 jeux’ by Pascal Naud, contained at least two of them, both classics, so I can reproduce them here without encountering copyright problems.

  1. 5 coins in a row*/*****

  2. Move 1 coin so that there are 5 coins in both rows,
    5 coins in a row exercise

    You can check your solutions here

  3. Pyramid*/*****

  4. Turn the pyramid upside down by moving 3 coins.
    Coins pyramid exercise

    You can check your solutions here

Many similar (and much more difficult) problems can be found on youtube.

  1. Move 3 coins to make a circle

At the beginning of the summer I was asked to become one of the elders in our church. It unfortunately means that I am not able to keep up the rate of a puzzle a week. Having a fair collection of posts in stock, I was able to keep posting puzzles weekly. But I’ve about run out of puzzles in stock. So be prepared there will be 2 puzzles a month from now on till the end of the year.

You are still welcome to comment on puzzles here, or to buy my book.

Bongard problem (9)

The Russian scientist M.M. Bongard published a book in 1967 that contains 100 problems. Each problem consists of 12 small boxes: six boxes on the left and six on the right. Each of the six boxes on the left conform to a certain rule. Each and every box on the right contradicts this rule. Your task, of course, is to figure out the rule.

Bongard problem 8**/*****
Bongard problem 34 exercise

You can check your solutions here

You can find more Bongard problems here and at Harry Foundalis site, and I intend to publish more problems in the future.

A new puzzle is published every Friday. Solutions are published after one or more weeks. You are welcome to remark on the difficulty level of the puzzles, discuss alternate solutions, and so on. Puzzles are rated on a scale of 1 to three stars.