Monthly Archives: November 2015

The river war


river war illustration

“It was during the Russian Civil War, ” Captain Abromovitch told his great grandchildren, “That I was ordered to take my ship, the Asbestos, down the river from Astrakhanitch to Cosmovitch. It was a valuable package I had to transport, and a dangerous mission as well, as the Tzarists still controlled Borovitch between Astrakhanitch and Cosmovitch. In Borovitch, the Tzarists held control of the Berilyum, a sistership of my Asbestos. Both had the same speed of 5 miles per hour on a lake without any current.”
He took a sip from his orange juice, and continued:
“They had a spy in Astrakhanitch, and this enabled the Berilyum to leave Borovitch to intercept me the minute I left Astrakhanitch with my Asbestos. Steaming upstream, of course the Berilyum went slower than my Asbestos steaming downstream, so we didnt meet in the middle between the two towns, but at a point closer to Borovitch than to Astrakhanitch. Having several soldiers on board, while I had none, they immediately seized my ship and brought us to Astrakhanitch.”

If the distance between Astrakhanitch and Borovitch is 20 miles, how long did it take the Tzarists to intercept the Asbestos?

You can check your solutions here

A new puzzle is posted every friday. You are welcome to comment on the puzzles. Solutions are added at the bottom of a puzzle after one or more weeks.

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Bongard problem (3)


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.

Here is an example:
Bongard problem 2015-09-17 nr 4 exercise

You can check your solutions here

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

The online exam


certificate illustration
This week I’ve got a quickie for you.
Last week I took an online certification exam. It was an open book certifiction, and I was free to consult the website and course map as often and as long as I wanted. Some types of questions scored 3 points, others scored 5 points.

My result was:
You scored 201 points out of 223 total possible points.
You answered 45 out of 51 questions correctly.

How many 5-point questions and how many 3 point questions did I miss?

You can check your solutions here

A new puzzle is posted every friday. You are welcome to comment on the puzzles. Solutions are added at the bottom of a puzzle after one or more weeks.

Inspector Simon Mart and the stolen toupet


2000px-Searchtool.svgInspector Simon Mart looked out of the window of his familiar office room. What he saw was very familiar: nothing. Or, more precisely: the well known grey of London smog. It looked like a particular dense smog, as he could not even see the tree at the other side of the street, nor the pedestrians or traffic in the street below.

He would much, much rather have been at the sun drowned beaches of a tropical archipellego, but he was here back in London.
And he’d better get to work. He looked at the interrogation reports of the three criminals. The toupet of major Big Boaster had been stolen. The three criminals were all so rotten that none of the three could utter three sentences without speaking the truth more than once. Luckily, it had already been established that one of them was the thief.

Their interrogation reports:
Picking Pete: Rotten Ray is innocent. Thoughtless Theo is the thief. I am innocent.
Rotten Ray: To his dismay inspector Mart found that some thoughtless secretary had spilled coffee over this interrogation report, and it was completely unreadable.
Thoughtless Theo: Picking Pete is innocent. I am innocent. Rotten Ray is the thief.

Inspector Simon Mart got himself some tea from the coffee maachine and found that it tasted just like one can expect from a coffee machine: the tea tasted as coffee.
Still, he managed to conclude who the thief was. Can you?

You can check your solutions here

A new puzzle is posted every friday. You are welcome to comment on the puzzles. Solutions are added at the bottom of a puzzle after one or more weeks.