## Archive for November, 2009

### Area of a triangle

Wednesday, November 18th, 2009

- What a nice parallelogram!
- I am glad you like it.
- What is that question mark doing in the center?
- I have tried to calculate the area of BQP, but so far without any luck.
- 6, 17, and 29 are the area of the triangles they are in?
- You are right. The problem is to find the area of the fourth triangle.
- Have you tried subtraction?

Problem source: The Emissary Spring 2009.

### Quote

Wednesday, November 18th, 2009

How well people communicate and work with people is more important than being up on the latest programming language. – Robert L Read

### Why now?

Tuesday, November 17th, 2009

Find two numbers that when added and subtracted give to perfect numbers.

### Quote

Tuesday, November 17th, 2009

Good people want to be hired for their skills, not where they worked last or what school they went to or some other inessential characteristic. – Robert L Read

Monday, November 16th, 2009

### Quote

Monday, November 16th, 2009

Do not train a child to learn by force or harshness; but direct them to it by what amuses their minds, so that you may be better able to discover with accuracy the peculiar bent of the genius of each. - Plato

### Reflections

Sunday, November 15th, 2009

GeoGebra is dynamic geometry software. Constructions can be made with points, vectors, segments, lines, polygons, conic sections, and functions. All of them can be changed dynamically afterwards. Elements can be entered and modified directly on screen, or through the command line. GeoGebra has the ability to use variables for numbers, vectors and points, find derivatives and integrals of functions and has a full complement of commands like Root or Extremum. Teachers can use GeoGebra to make conjectures and prove geometric theorems. – More

Let your students guess and play around with their guesses. Most schools can afford the software. It is free.

### Playful thinking

Saturday, November 14th, 2009

If tug of war is your kind of war and you can’t get enough of subtracting decimals then click here.

### Memory leak

Friday, November 13th, 2009

The other day I sold two books I bought a few years back. One of them gave me a 20% profit, while the other gave me a 20% loss. Together, however, the two books gave me a 5% profit.

I can’t seem to remember how much I sold each bok for, although I do remember that the total sale price was 1260 baht.

Problem source: Rudi Kessel, Mattenøtter.

### Quote

Friday, November 13th, 2009

An eye for an eye will only make the whole world blind. - Mohandas Gandhi