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IntMath Newsletter: Prime cicadas

By Murray Bourne, 30 Apr 2013

30 Apr 2013

In this Newsletter:

1. Math resource: MathGraph32
2. Prime numbered cicadas
3. Relieving test anxiety
4. Math puzzle
5. IntMath Poll
6. Final thought:

Once again I apologize for the long gap since the last IntMath Newsletter. I'm involved in several large projects (including developing online modules for a math course and 2 academic integrity courses). Once those are done, hopefully I'll be able to get back to a regular schedule of writing.

1. Math resource: MathGraph32


MathGraph32 is a great free tool for exploring 2D and 3D math concepts.


2. Prime numbered cicadas


The 17-year cicada is due to emerge in north-eastern parts of USA in Spring 2013. What is their connection to prime numbers?

Prime numbered cicadas

3. Relieving test anxiety

Annie Murphy Paul writes the Brilliant Report for Time magazine, It's an interesting collection of research about the brain and how to squeeze more out of it.

A recent article, How to Eliminate Test Anxiety gives some good pointers, which as she says, are reasonably simple, inexpensive and, as recent studies show, effective."

Here's some short quotes from her list of suggestions:

1. Unload on paper. Spend ten minutes writing about your thoughts and feelings immediately before taking a test.

The practice, called "expressive writing," is used by psychologists to reduce negative thoughts in people with depression. They tried the intervention on college students placed in a testing situation in Beilock’s lab, and in an actual Chicago school, where ninth-grade students engaged in the writing exercise before their first high school final. In both cases, students’ test scores “significantly improved,” according to an article they published last year in the journal Science.

2. Affirm your values. Apprehension over tests can be especially common among minority and female students. That’s because the prospect of evaluation poses for them what psychologists call "stereotype threat"—the possibility that a poor performance will confirm negative assumptions about the group to which they belong ([this posits] that girls can't excel in math and science; blacks and Latinos aren’t college material).

3. Engage in relaxation exercises. Younger kids aren’t immune from test anxiety. As early as first and second grade, researchers see evidence of anxiety about testing. Their worries tend to manifest in non-verbal signs that adults may miss, [like] stomachaches, difficulty sleeping, and a persistent urge to leave the classroom to go to the bathroom.

(From The Brilliant Report: How To Eliminate Test Anxiety)

4. Math puzzles

The puzzle in the last IntMath Newsletter was about expressing the number one using nines, a minus sign and dots.

Correct answers were given by dalcde, Christopher, Bonnie, Andrzej, Dineth, Nicos and Thomas.

Math symbols were a challenge: I knew it was going to be tricky to type in the answers for this puzzle. I started to write some pointers about how to do it and stopped, because that would have given the answers away! (There is a "Preview" button on the response box for the blog. You can use it to make sure your math looks OK before posting.)

  1. Superscripts (powers): You can create a superscript by typing it like this in the "Respond" box of most blogs:

    9<sup>9-9</sup> = 1

    It will look like this:

    99-9 = 1

  2. Dot above a number: This one is a bit trickier, as there is no HTML solution that works nicely in all browsers. The best way is to create an image using a tool like Codecogs Equation Editor. It has a visual interface, but requires some knowledge of LaTex. You need to enter:

    0.\dot{9} = 1

    At the bottom of the equation editor page there is an "embed" box with code. Copy that code into the "respond" box in most blogs and it will look like:


Note 1: I included the "0" before the decimal point in my answer above. A lot of people don't notice the dot, and misread decimal numbers. (Yes, I know the question specified "one nine" only, but it's worth mentioning.)

Note 2: I was aware the question was somewhat country-specific. The Europeans write a decimal number using a comma, not a dot.

And as Andrzej pointed out in his response regarding the recurring part:

There are three symbols for recurring fractions: dash, dot (UK and USA) and () in Poland. So the solution is slightly tricky; it depends on nationality.

It would be really nice if we had consistent math notation around the world, especially when for something as simple as writing numbers!

New puzzle: 216 cubes of side length 1 cm are arranged to make a cube with side length 6 cm.

A sphere of diameter 6 cm is inscribed in the large cube such that the center of the sphere is the center of the cube. How many complete unit cubes is contained in the sphere?

You can leave your responses here.

5. Final thought: Watching

Donald Trump is a real estate millionaire who became quite famous as a result of his role in the TV series The Apprentice. He once said:

Work hard. Someone's always watching.

Until next time, enjoy whatever you learn.

See the 15 Comments below.

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Comment Preview

HTML: You can use simple tags like <b>, <a href="...">, etc.

To enter math, you can can either:

  1. Use simple calculator-like input in the following format (surround your math in backticks, or qq on tablet or phone):
    `a^2 = sqrt(b^2 + c^2)`
    (See more on ASCIIMath syntax); or
  2. Use simple LaTeX in the following format. Surround your math with \( and \).
    \( \int g dx = \sqrt{\frac{a}{b}} \)
    (This is standard simple LaTeX.)

NOTE: You can mix both types of math entry in your comment.


Tips, tricks, lessons, and tutoring to help reduce test anxiety and move to the top of the class.