thnik again!

- I can tell how old you are.
- No, you can’t.
- How many times will 10 go into your age?
- I won’t tell you!
- No problem. Take the number and multiply it by 5.
- OK.
- Add 3.
- OK.
- Double it.
- OK.
- Add the last digit of your age to the result of the addition.
- OK.
- Subtract 6.
- OK.
- What number do you have now?
- My age!
- What is it?
- I told you: I won’t tell you.

When I was a kid, 13, I was amazed by ‘tricks’ like these. Find some kids and watch their reaction. Are they amazed, bewildered, or bored? Can they explain how the trick works?

Problem source: http://www.mathconcentration.com/

- For Christmas I got a pool table.
- Really?! Does it fit in your apartment?
- It is just a miniature version. It fits on the dining table.
- I see.
- I have been losing constantly to my young son.
- I am not surprised.
- The 15 balls are numbered 1-15. The first one to pocket a ball will try to pocket balls of the same parity.
- Translation please!
- If I pocket 4 I will get the even balls, but if I first pocket 11 I will get the odd balls.
- What about ball 8?
- When someone has pocketed all his ball he has to pocket the 8 ball to win.
- I see.
- It is a nice game!
- Now I know why you may have lost a lot.
- But you haven’t even seen me play!

- I am thinking of a number.
- Any number?
- It is prime.
- I was once in my prime.
- It is the smallest prime number that is equal to the sum of two prime numbers
and is also equal to the sum of three different prime numbers.
- Really?! It is the same as my house number!

A two-digit number is seven times greater than the sum of its digits.

“Around 20 years ago, a scientist named Scott Feld was looking at a survey of teenagers and their friends. He looked at the total number of friends one student had, and then looked at the average number of friendships those friends had. After repeating this experiment over and over, he came to a startling conclusion. For most people, their friends were more popular, on average, than they were. He puzzled over the result, and then came up with a very neat explanation.”

Please, do the same!

Source: maths + stats by email by http://www.csiro.au.

In which region of the table may I put ball B so it can be hit by ball A when it rebounds from the upper and right side?

Problem source: Estímulo del Talento Matemático.

- I want to shoot the billiard ball A so it hits B.
- That shouldn’t be too difficult.
- A has to rebound from two of the sides before it touches B.
- What is the shortest route?
- Exactly!

Problem source: Estímulo del Talento Matemático.

How far is it from A to B along the surface of the cylinder?

Problem source: Estímulo del Talento Matemático.

What is the shortest route to the road L when you have to get some water from the river at M first?

Problem source: Estímulo del Talento Matemático.

- I want to find the shortest way from A to B.
- But please remember you have to visit the lines L and M on your way!
- How could I forget?!
- By the way, does it matter if you visit M before L or L before M?
- Of course not!

Problem source: Estímulo del Talento Matemático.