Using distinct 2-digit numbers from 11-99 that have no zeros, fill in the grid so that the tens digits form a Sudoku and the units digits form a (different) Sudoku. There might be a mathematical way to solve this problem since I found it in a fun math book.

Suppose we have 4 by 4 grid with numbers 1, 2, .., 16. Can we fill the grid so that the product of the first row is equal to the product of the first column, the product of the second row is equal to the product of the second column, ..., etc? I have already gotten answer here for n=5: Fill in a ...

So my friend ask me to look for what kind of code or cipher or anything this thing is, and I have been researching for a while now without any luck. The code: ++ ×× -- / ×= ×÷ -- -÷ / -= ×÷

There are 6 boxes, each containing a distinct number. You can select 3 boxes and the Oracle will tell you which box has the smallest number and which has the largest number of the three selected boxes. Can you use 6 steps (selections) to work out the exact order of numbers in each box, from small...

The enlightened but, sadly, fictional country of Switzerland has it all: A strong democracy that rejects centralism, a reliable public transport network and its own version of chess. Swiss chess reflects the values of the Swiss and does not tolerate the obsession with the centre that has so discr...

Earlier, I introduced the beautiful game of Swiss chess. Unlike the peace-loving Swiss, we are interested in "domination", the art of threatening or occupying every square of the board using a given set of pieces, four Swiss queens for this puzzle. But how to persuade four pacifist queens to do s...

Draw a shape consisting of all the points equidistant from a specific point. Furthermore, draw a segment passing through a side of the shape exactly twice, and draw another segment so that it also passes through the shape exactly twice, but intersects with the other segment at one of the points w...