## Wednesday, June 17, 2009

### My Special Number: 25

For many years I assigned an end-of-unit project to my sixth graders titled My Special Number. This was when students would pick a number on which to perform a number study. Today I offer my own version of this assignment.

My special number is 25. It is a number that is described as odd, composite, and square. It is odd because it is not divisible by two. It is composite because its factor pairs are not only 1 x 25, but also 5 x 5. Having 5 x 5 as a factor pair is also what makes it a square number. In fact it is the smallest square number that is the sum of two other square numbers. ( 9 + 16 = 25) This relationship is found in many right triangles (known as 3-4-5 triangles) used for illustrating the Pythagorean Theorem.

Because 25 is a factor of 100, it is used in a variety of ways. A twenty-five cent coin is a quarter and it takes four to equal a dollar. 25% is equivalent to ¼.

The number 25 has significance in various religions and philosophies. According to Abellio, twenty-five is the symbol for the Universal Word of God. St. Augustin used it to represent the law. In the Bible, King Solomon builds a temple to God that is 25 cubits high, and a Levite could begin practicing his ministry at the age of twenty-five.

But today, the number twenty-five has a special significance. Today marks the day that indicates that FOR TWENTY-FIVE WONDERFUL YEARS I HAVE BEEN MARRIED TO THE BEST HUSBAND I COULD POSSIBLY HAVE!

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## 2 comments:

I love the project! I wish I had thought of it when I taught sixth grade math. Congratulations on your 25th wedding anniversary. It sounds like you are very happy!

I can't really take credit for the project per se. It came from the Connected Middle School Math book Prime Time. Over the years, some of my students had some great projects. Thanks for the anniversary wishes--I am very happy!

Marsha

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