Dice Game

 

 

Sorting Numbers

 

 

1. Arrange the digits 1-9 in a line so that each pair of adjacent digits differs by either 2 or 3.
2. Arrange the digits 1-9 in a line so that each pair of adjacent digits sums to a prime number.
3. Now arrange the digits 1-9 in a line so that each pair of adjacent digits (when read as a two-digit number) appears in the times tables from 1 × 1 up to 9 × 9.

 

 

 

        Source: Katie Steckles, The New Scientist

Guess the number

 

Ask a friend to pick a number from 1 through 1000. After asking him 10 questions that can be answered yes or no, you tell them the number. What kind of questions should you ask your friend so that you find their number? 

Source: Kordemsky, The Moscow Puzzles