Issue 1Jan 2023

Roman Numeral

David Pleacher1998

Which year in history has had the greatest number of Roman Numerals in it? What year will this record be surpassed?


Naoki Inaba2009

Fill in each empty cell with either an O or an X, so that no more than two consecutive cells, either horizontally, vertically, or diagonally, contain the same symbol.

Marupeke puzzle

Kant's Clock

Martin Gardner1961

It is said that Immanuel Kant was a bachelor of such regular habits that the good people of Königsberg would adjust their clocks when they saw him stroll past certain landmarks.

One evening Kant was dismayed to discover that his clock had run down. Evidently his manservant, who had taken the day off, had forgotten to wind it. The great philosopher did not reset the hands because his watch was being repaired and he had no way of knowing the correct time. He walked to the home of his friend Schmidt, a merchant who lived a mile or so away, glancing at the clock in Schmidt's hallway as he entered the house.

After visiting Schmidt for several hours Kant left and walked home along the route by which he came. As always, he walked with a slow, steady gait that had not varied in twenty years. He had no notion of how long this return trip took. Schmidt had recently moved into the area and Kant had not yet timed himself on this walk. Nevertheless, when Kant entered his house, he immediately set his clock correctly.

How did Kant know the correct time?

Japanese Temple Geometry

Fukagawa, H. and D. Pedoe1989

Find the side length of the internal square and the radii of the internal circles, in terms of a.

Japanese Temple Geometry puzzle

Monkey and the Coconut

Ben Ames Williams1926

Five men and a monkey were shipwrecked on an island. They spent the first day gathering coconuts. During the night, one man woke up and decided to take his share of the coconuts. He divided them into five piles. One coconut was left over so he gave it to the monkey, then hid his share, put the rest back together, and went back to sleep.

Soon a second man woke up and did the same thing. After dividing the coconuts into five piles, one coconut was left over which he gave to the monkey. He then hid his share, put the rest back together, and went back to bed. The third, fourth, and fifth man followed exactly the same procedure. The next morning, after they all woke up, they divided the remaining coconuts into five equal shares. This time no coconuts were left over.

How many coconuts were there in the original pile?