Chance for a Would-be Bride

girl-straws There was a tradition in old Russia. A would-be bride gathers six long pieces of straw and grasp them in her hand. She then randomly ties pairs of knots on the top and the bottom. Since there are six blades of grass sticking out above and below the hand, she will tie three knots on the top and three knots on the bottom. If she forms one big ring, she gets married soon.

Estimate the probability that the girl will get married soon.

The problem is mentioned in The New York Times NUMBERPLAY and it is credited to Sunil Singh.

Answer

Secret Agent 007

Seven secret agents are on payroll of a government.

Secret agent 001 spies on a secret agent who spies on secret agent 002,

who spies on a secret agent who spies on secret agent 003,

who spies on . . . spies on secret agent 007

who spies on a secret agent who spies on secret agent 001.  

Who spies on secret agent 007?

AplusclickSecretAgent007

Answer

 

18 Best Aplusclick Puzzles of 2018

New challenges:

What is the easiest way to make it correct?            Answer

AplusclickCOrrectEquation

In what Olympic sport does the winner cross the line facing backwards?      Answer

AplusclickBackward

What time is it?         Answer

AplusclickClockFall

What is the necessary mirror size?     Answer

AplusclickGirlMirror

Find all 18 best puzzles at

Is Zero Your Hero?

Everybody has a favorite number.  What number is your hero?

Not Knowing Math Can Cost $15,000

 

A big number of people can lack basic math skills.

Mystic Number 7

aplusclicksevenplanets

Why we frequently use number 7?

Why there are seven days of week? seven deadly sins? seven wonders? . . . .

Look for the answer in the night sky or at aplusclick.org

Classics of Recreational Math

The classical recreational math authors are Lewis Carroll,  Henry DudleyMartin GardnerSam Loyd, and Yakov Perelman.

This an example of classical math puzzles: https://www.aplusclick.org/k/5423.htm :

(102 + 112 + 122) – (132 + 142) = ?

The picture “Mental Count” of Russian painter Nikolay Bogdanov-Belsky contains the simple calculation. Image source : Wikipedia

427px-BogdanovBelsky_UstnySchet

 

The logic puzzle almost everyone gets wrong

This is a very famous logic problem:

“Jack is looking at Anne, but Anne is looking at George. Jack is married, but George is not. Is a married person looking at an unmarried person?

  • A: Yes
  • B: No
  • C: Cannot be determined”

married

According to the Keith E. Stanovich in Scientific American more than 80 percent of people choose C, which is not the correct answer. The correct answer is A. Why?

This is another example of a similar problem:

There are only two handshakes in a meeting: John shakes hands with a person, this person shakes hands with Anna. Does a man shake hands with a woman in the meeting?

Answer

Extraordinary Math Teaching by Dan Finkel

Dan Finkel suggested principles of extraordinary math teaching:

Math can the best of time or the worst of time.

 

 

1) Start with a question.

2) Thinking happens only when you have time to struggle.

3) (Teacher), you are not the answer key.

4) Say yes to your students’ ideas.

5) Play!

A marvelous quotation is attributed to the most brilliant scientist of the modern age, Albert Einstein: “Play is the highest form of research.”

 

 

 

How to Solve a Problem – Read the Question

Try to solve the following problem suggested by Leslie Green:

cases

What is the difference between the number of letters in UPPER CASE and lower case in the text?

Most of the people and me too answered the question fast: None.

If you give the same answer, read the question again.

The trivial advice is often useful: “Try to answer exactly to the question.”

Do you get another answer? What is it?

1932Another example:  A shopkeeper of a Dairy stands six feet tall and wears size 13 sneakers. What does he weigh?