## Mystic Number 7

May 7, 2017 Leave a comment

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

Math and Logic Puzzles

May 7, 2017 Leave a comment

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

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June 10, 2016 Leave a comment

The classical recreational math authors are Lewis Carroll, Henry Dudley, Martin Gardner, Sam Loyd, and Yakov Perelman.

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

(10^{2} + 11^{2} + 12^{2}) – (13^{2} + 14^{2}) = ?

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

April 23, 2016 1 Comment

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”**

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?*

April 10, 2016 Leave a comment

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.”

February 3, 2016 Leave a comment

Try to solve the following problem suggested by * Leslie Green*:

*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?

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

February 26, 2015 Leave a comment

February 3, 2015 Leave a comment

Find the area of the rectangle if the numbers show the areas of the corresponding triangles.

Find the area of the shape.

How many squares of all different sizes are on a chessboard?