Tuesday, September 10, 2024
Sunday, May 12, 2024
Sorting Numbers
- Arrange the digits 1-9 in a line so that each pair of adjacent digits differs by either 2 or 3.
- Arrange the digits 1-9 in a line so that each pair of adjacent digits sums to a prime number.
- 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
Friday, April 12, 2024
Monday, February 5, 2024
Sunday, January 21, 2024
Monday, December 25, 2023
Palindromic times
A time such as 3:59:53 is palindromic, that is, it reads the same forward and backward. in a day starting from 0:00:00 to 23:59:59, there are 660 occasions when the time is palindromic. Among them which of the two is closest?
Source: Nobuyuki Yoshigahara
09:59:59 and 10:00:01
Cutting Puzzle
This lovely puzzle is from professor Tanya Khovanova's blog.
You are given a 5-by-7 rectangle with two corners cut out: A 1-by-1 tile is cut from the bottom left corner, and a 1-by-2 tile is cut out of the top right corner, as in the picture. The task is to cut the resulting shape into two congruent polyominoes.
Monday, May 15, 2023
Tuesday, February 21, 2023
Tuesday, January 31, 2023
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