thnik again!

- What a nice car you got!
- I am glad you like it.
- I like the license plate even more than the car!
- Why so?
- The license plate ends in 2010. If you remove those four digits the original number is divisible by the new one.
- I don’t understand what you mean.
- The license number is 2012010 which gets reduced to 201.
- Are you suggesting that 201 goes into 2012010 a whole number of times.
- Absolutely!
- But that will happen to millions of license plate number that ends in 2010, won’t it?
- Not exactly.

We believe we are the only species who believes we are the only species who is intelligent. – Jan Nordgreen

Play proceeds to the left around the table. On your turn, you may flip two cards face up. If one of the cards is a 10, you may take it at once and flip another card face up. If the pair of face-up cards add together to make 10, you get to take the pair. If they do not make 10, leave them for a few seconds so all players can see what they are, then turn them face down and let the next player take a turn.

Full rules for Tens Concentration is at Let’s Play Math: “Math is a game, playing with ideas. This blog is about learning, teaching, and just playing around with K-12 mathematics. Have fun!”

- Do you know the square root of 121?
- Not personally, but I believe it is 12.
- A friend of mine has found a number whose square root is a surprise.
- To his Mom?
- No Einstein! To his math teacher.
- Really?
- After the 13th digit after the decimal point it starts to repeat itself.
- Like my math teacher, only he does it earlier!
- Very funny!
- How does it repeat itself?
- He didn’t want to tell me the number, but it repeats itself like …183902183902183902183902…
- Really!? I find that hard to believe.
- I told you it was not to be expected.

Problem source: The Endeavour. The blog of John D Cook.

How can a door be less squeaky than before, but not squeak less? – Jan Nordgreen

- Do you know what a semiprime is?
- If I concentrate I may remember what a prime is.
- 21 is a semiprime since it is the product of two prime numbers.
- You mean 3 and 7?
- 22 is also a semiprime.
- Get out of here!
- 2 and 11 gives 22.
- Are there more pairs of consecutive numbers that are semiprimes?
- There is one pair before 21 and 22.
- And after?

Problem source: math hombre.

Mathematics education is much more complicated than you expected, even though you expected it to be more complicated than you expected. – E G Begle

Use the digits in the year 2010 to write mathematical expressions for the counting numbers 1 through 100. All four digits must be used in each expression. You may not use any other numbers except 2, 0, 1, and 0. You may use the arithmetic operations +, -, x, ÷, sqrt (square root), ^ (raise to a power), and ! (factorial). You may also use parentheses, brackets, or other grouping symbols. You may use a decimal point to create numbers such as .1, .02, etc. Multi-digit numbers such as 20 or 102 may be used, but preference is given to solutions that avoid them. Bonus Rule: You may use the overhead-bar (vinculum), dots, or brackets to mark a repeating decimal.

The problem is from Let’s Play Math. Are you game?

Polya has become the Marx and Lenin of mathematical problem solving; a few words of obeisance need to be offered in his name before an author can get down to the topic at hand. – Jeremy Kilpatrick