(from Boris Kordemsky - The Moscow Puzzles)
Thursday, December 31, 2020
Monday, December 21, 2020
Sunday, December 20, 2020
Thursday, December 17, 2020
12 Days of Christmas
If we choose three gifts randomly, what is the probability that they are all birds of the same kind?
Saturday, December 5, 2020
Friday, December 4, 2020
Average Pages
Mother asked Vera to type a manuscript. Vera decided: "I will type an average of 20 pages a day."
She typed the first half of the manuscript rather lazily, at 10 pages a day. To make up for it, she typed the second half at 30 pages a day.
"See, I did average 20 pages a day," Vera concluded. "Half of 10 + 30 is 20."
"No, you didn't," her mother said.
Who was right?
Wednesday, November 25, 2020
Monday, November 16, 2020
Thursday, November 12, 2020
Tuesday, November 10, 2020
Forming Equations - Bingo
When a number is increased by 5, the answer is 7.
When a number is decreased by 3, the answer is -1.
When a number is increased by 5 and the resulting number is doubled, the answer is 33.
A number is doubled and three is added. The result is 7.
Twice a number is 3 less than the number.
Four times a number is equal to 35 minus the number.
3 added to the square of a number is 7.
Two consecutive numbers are added and the answer is 21.
Two consecutive even numbers are added and the answer is 14.
Three more than a number is two.
A number subtracted from seven is equal to three more than that number.
Monday, November 9, 2020
Multi-step Equation Challenge
Using the digits 1 to 9, at most one time each, create an equation where x has the smallest (or greatest) possible value.
Source: Open Middle
Tuesday, November 3, 2020
A Surprising Matchstick Puzzle
Resource: Puzzle A Day
Friday, October 30, 2020
Wednesday, October 28, 2020
Tuesday, October 27, 2020
Monday, October 26, 2020
Parallel Parking
Every weekend, I drive into town for contactless curbside pickup at a local restaurant. Across the street from the restaurant are six parking spots, lined up in a row.
While I can parallel park, it’s definitely not my preference. No parallel parking is required when the rearmost of the six spots is available or when there are two consecutive open spots. If there is a random arrangement of cars currently occupying four of the six spots, what’s the probability that I will have to parallel park?
Source:The Riddler
Three Die Together
Three die are randomly put together as shown above.
What is the probability of the visible face totaling to 13?
In the example above the total is 3+4+5=12
Sunday, October 25, 2020
Saturday, October 24, 2020
Friday, October 23, 2020
Thursday, October 22, 2020
Thursday, October 15, 2020
100% Saving
One invention saves 30% on fuel; a second, 45%; and a third, 25%. If you use all three inventions at once can you save 100%? If not, how much?
resource: The Moscow Puzzles, Boris Kordemsky
Wednesday, October 7, 2020
Monday, October 5, 2020
Rock-Paper-Scissor Puzzle
Start in any square and move one square at a time straight or diagonally. You can only move to a square that you can beat. Eg you can move from scissors to paper as scissors beats paper. Once you've been to a square, you can't return to that square. How can you visit each square?
Start in any square and move one square at a time straight or diagonally. You can only move to a square that you can beat. Eg you can move from scissors to paper as scissors beats paper. Once you've been to a square, you can't return to that square. How can you visit each square? pic.twitter.com/X3mzYX8Jor
— Puzzle a Day (@PuzzleADayBlog) October 4, 2020
Monday, September 28, 2020
Angles on the clock
What is the acute angle between the hour and minute hands?
What time will it be when the same angle occurs for the first time after 10:10?
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