If you add all the substrings of 891, the sum is 198, which is the reverse of 891: 891 → 8 + 9 + 1 + 89 + 91 = 198 This is the only 3-digit number that has this property. There is also one 4-digit number with the same property. Can you find this […]

One day, when a speaker was introducing logician and puzzlist Raymond Smullyan, he remarked that “Professor Smullyan is unique.” Smullyan, who was feeling playful that day, said, “I’m sorry to interrupt you Sir but I happen to be the only one in the entire universe who is not unique.” On another event, Smullyan was introduced […]

Horace Walpole (1717-1797) sent the following riddle to Lady Ossory, claiming that it was composed by physicist and mathematician Isaac Newton: Four people sat down at a table to play; They play’d all that night, and some part of next day; This one thing observ’d, that when all were seated, Nobody play’d with them, and […]

In the September 29, 1888, edition of Weekly Wisconsin, the following strange enigma appeared, composed by an anonymous writer named “Maude”: Perhaps the solvers are inclined to hiss, Curling their nose up at a con* like this. Like some much abler posers I would try A rare, uncommon puzzle to supply. A curious acrostic here […]

Using the digits 1, 2, 3, 4 twice, form an eight-digit number in such a way that there is one digit between the 1’s, two digits between the 2’s, three digits between the 3’s and four digits between the 4’s.

Here is a very simple match puzzle. Move just a single match to form a perfect square. This is indeed an easy puzzle. However, there are two ways to solve this and the solution depends on who’s solving the puzzle.

What is the smallest rectangle which can be made by using jigsaw pieces of these two shapes only? What is the next smallest such rectangle? What rectangles are possible using these shapes only? (Note: You can use no matter how many of these two jigsaw pieces as you see fit.)

Lay out six matches in the way depicted in the illustration. The objective is to shift one match without displacing the others so that the resulting arrangement would represent an arithmetical fraction equal to 1. You are not allowed to move the match forming the horizontal fraction bar.