thnik again!

Classic “concentration” game — behind each tile is an image. They are 12 familiar things you’d see at the beach. Click on a tile to turn it over and reveal an image. Then select a second tile, trying to find the matching image. If the images match, the tiles are removed from the board. Try to see how few turns you need to remove all of the tiles. A great score is 18-25, a good score is 26-30, over 30 — try again! – Play it here.

I needed 38 turns, which made me think: How many turns are needed if you cheat, i.e. if you write down every card you look at?

To factorise numbers can be done amazingly fast with a dumb algorithm on a computer. Run over to http://www.cryptographic.co.uk/factjava2.html by Andrew Hodges and see what patterns you discover with your favourite number.

http://www.cryptographic.co.uk/factorise.html gives a bit more background.

I was born in 1952. If you turn it partly upside down and read it from right to left you get 2⁵x61 = 1952.

Martin Gardner has turned thousands of children into mathematicians, and thousands of mathematicians into children. – Ronald Graham

The Math Mom suggests a novel way for assigning courts to tennis players here. What do you think of it?

If God creates a world of particles and waves, dancing in obedience to mathematical and physical laws, who are we to say that he cannot make use of those laws to cover the surface of a small planet with living creatures? – Martin Gardner

A: 65 92 74 14 56 29

B: 15 22 61 27 82 72

What do the numbers in A have in common that is not shared by the numbers in B.

If that was too easy, try this one:

A: 89 41 56 65 24 84

B: 39 94 46 35 74 11

Problem source: Pradeep Mutalik in Tierney Lab, New York Times.

Did Adam and Eve Have Navels? – Martin Gardner

Move two of the nine toothpicks to turn 100 into CAT.

Problem source: Martin Gardner.

Biographical history, as taught in our public schools, is still largely a history of boneheads: ridiculous kings and queens, paranoid political leaders, compulsive voyagers, ignorant generals – the flotsam and jetsam of historical currents. The men who radically altered history, the great scientists and mathematicians, are seldom mentioned, if at all. – Martin Gardner

Here is a giraffe made with five toothpicks. Move just one of them to get the same giraffe, turning somewhere else.

Problem source: Martin Gardner, who was 95 years last week.