# Featured

## Mind Benders: Numbers with Clues (April 11-14)

Mind Benders challenge the children to look at a number critically and think of it in the context of certain clues.

For example, the number 26 is best known by English speakers as the number of Letters in the Alphabet. So the clue "26 L in the A" usually triggers the association. Another easy one is "365 D in a Y."

The first sheet attached are 25 Mind Benders I created with math in mind. The second one is more challenging and should be attempted with the whole family. Try not to look at the solutions.

## Mobius Strip (April 4-7)

We explored the simplest geometric shape with one face and one edge. The paradox is that this is a three dimensional polyhedra. It has revolutionized belts for engines and has been used to define black holes. I proved to the children that a conventional fan belt in an engine or computer only uses one side of the belt and wares out quickly. A Mobius belt uses twice the surface area and lasts twice as long.

## Four Color Map Theorem (March 28-31)

Francis Guthrie, a 21yearold mathematics student at University College in London, was mapping the counties of England in 1852 when he noticed that he only needed four colors for the map. He asked his younger brother, Frederick Guthrie, if this was true for any map. Frederick took the problem to his professor, Augustus de Morgan.

## Coordinate Plane Graph Pictures (March 21-24)

Mathletes had fun this week with their coordinate pictures. We introduced all four quadrants in the coordinate plane.

## Sir Cumference and the Dragon of Pi (March 14-17)

Pi day is upon us again as Monday was March 14. It is called Pi day because the number Pi starts with 3.14. We challenged the Mathletes to think of what 2Pi day would be; calculating 6.28, they say, "June 28." Then 3Pi day is fun; 9.42 gets them thinking about 30 days in September, so some of them go into October 12th. A silly past-time but fun.