## Monday, June 30, 2008

### SIR "OY", E. NOET! Our July Mathanagram!

SIR "OY", E. NOET!

Laboring over the anagram of our Mathematician of the Month for hours, then having someone unscramble it in a few nanoseconds...

Oh well, I hope you enjoy this one. Remember there are rules which I will summarize below. To add to the usual requirements, you need to show how our Mathematician is somehow connected to our preceding star, thereby unlocking the hidden code in the puzzle. Otherwise all my efforts would be wasted!

• Remember to email me at dmarain at geeeemail dot com
• Pls pls use Mystery Mathematician July 2008 in the subject line!

(1) The name of the mathematician
(2) Some interesting info/anecdotes re said person
(2.5) Explain the code embedded in the anagram!
(4) Your full name and the name you want me to use when acknowledging your accomplishment
(5) If you're new, how you found MathNotations

## Sunday, June 29, 2008

### Probability and Counting Challenge -- You'll Need To Sit Down for This One

Five people with first initials A, B, C, D and E were seated randomly in a row in a movie theater with no spaces between them. What is the probability that A, B and C were adjacent to each other in some order? (For example: "DBACE")

A potential SAT problem or is it a level above? A math contest problem or not difficult enough? More importantly, how much experience do most of our students have with these kinds of combinatorial problems? I know that some of our educators who visit here do these with their classes, but is it the norm? My feeling is that students need to see many of these developed over time in more than one course.

What method (s) do you consider the most effective for solving these kinds of problems? For teaching? Are these 2 questions really the same?

After this question is discussed with the class, how does the instructor assess the learning? Give them another one to try immediately or give a worksheet of these (if the text does not provide enough practice)? How could one raise the bar even higher?

Suggested Extension #1: This time we have 10 people seated randomly in a row (no spaces). What is the probability that 4 of them, say A. B, C and D, would be adjacent to each other?

Suggested Extension #2: N people seated randomly in a row (no spaces). What is the probability that a particular subset of M of these people would be adjacent to each other?

## Sunday, June 22, 2008

### MEN-Y THEOREM? EMMY NOETHER REVEALED!

I could say so much about Emmy, but our four winners this month have said it much better and have provided some excellent links. Some of my personal thoughts about Emmy are given at the bottom, in my reply to Alex.

If you like the idea of an occasional anagram, let me know. Creating meaningful anagrams out of mathematicians' names can be formidable (certainly time-consuming!).

Our winners are...

HYPATIA

Hi Dave,
I wasn't going to write, but I just couldn't pass this one up! I suppose a picture would give it away, so the anagram was a clever trick. I must say, it's about time -- a woman mathematician! And what a great one --Emmy Noether.
Now let's see - an anecdote. Well we could say that her obituary for the New York TImes was written by none other than Albert Einstein.

http://www-history.mcs.st-and.ac.uk/Obits2/Noether_Emmy_Einstein.html

For a short little bio, here's the following from http://faculty.evansville.edu/ck6/bstud/noether.html

 Within the world mathematical community, Emmy Noether is widely regarded as the greatest of all woman mathematicians. She was born in the German university town of Erlangen, where her father, Max Noether, was a professor of mathematics. After receiving the Ph.D. degree from the University of Erlangen under Paul Gordan, Dr. Noether moved to the University of Göttingen, known in those days as the Mecca of Mathematics. There she developed as a world-class algebraist and taught a number of doctoral students who eventually became leading algebraists. Noether came to the United States in 1933, where she taught at Bryn Mawr College near Philadelphia and lectured at the Institute for Advanced Study in Princeton, New Jersey. Emmy Noether's name is known to many physicists through Noether's Theorem, described by Peter G. Bergmann as a cornerstone of work in general relativity as well as in certain aspects of elementary particles physics. For details, see Brewer and Smith, page 16. Her name is known to mathematicians largely in connection with the adjective noetherian, which applies in ring theory to properties associated with ascending chains of subrings. Specifics are given in Brewer and Smith, page 18.

It is probably true that most algebraists have never heard of Noether's Theorem in physics and that most physicists have never heard of noetherian rings.

But to do her justice, I'll also include the following links:

http://www.physics.ucla.edu/~cwp/Phase2/Noether,_Amalie_Emmy@861234567.html

http://www.sdsc.edu/ScienceWomen/noether.html

http://www-history.mcs.st-and.ac.uk/Biographies/Noether_Emmy.html

FInally, I love anagrams, actually puzzle of all kinds. So thanks for this one.

Hypatia

------------------------------------------------------

P. Miller

1. Emmy Noether
2. Worked for years w/o compensation
------------------------------------------------------

TC--

Hi Dave,

I thought the name had to have a hyphen - after that wild goose chase,
I managed to find the name of Emmy Noether.

Interesting Anecdote; There is a lunar crater named for her (and for
many other mathematicians, I find!)
Also, her obituary in the NY Times was written by Einstein.
------------------------------------------------------

ALEX DAVIES

(1) The name of the mathematician

Emmy Noether

(2) Some interesting info/anecdotes re said person

Emmy was a brilliant mathematician who struggled for recognition from university authorities, because of her sex. Other mathematicians could see her talent, though - she was mentored by Hilbert, who said "she is superior to me in many respects."

Late in her life, she taught in a girls' school in Pennsylvania. "The New York Times printed a short obituary, as it always did when a Bryn Mawr teacher died, but shortly thereafter, they printed a long letter to the editor pointing out that Emmy Noether had not only been a teacher at a girls' college, but the greatest woman mathematician of all time," wrote Freund in a book. "The letter was signed: Albert Einstein."

Acting on your hint, I googled "First female mathematicians," which took me to this top ten, on which Emmy was tenth.
Here is the quote from Hilbert.
Here is the end quote.
-------------------------------------------------------------------------------------------

By the way, here was my reply to Alex, which pretty much expresses my view of Emmy:

Thank you, Alex. It sure was nice of ol' Albert to acknowledge Emmy as the greatest 'woman' mathematician of all time. Imagine if some day, Emmy is recognized as the greatest mathematician/physicist of all time! Perhaps she would have acknowledged Albert as one of the best of his gender!!

## Tuesday, June 17, 2008

### SOMETHING NEW! Instructional Strategy Series: Teaching Average Rates

The following is the first in a series of strategies for teaching concepts that often prove difficult for many students from middle school on. These are not based on carefully controlled research studies following clinical methodology for a dissertation. They are based on 30+ years of learning how to do it better!! I suspect that's why we refer to the practice of teaching. Our readers are encouraged to share their own favorite methods that have been helpful to their students or to themselves. These ideas are intended only as suggestions. Each teacher will, of course, bring her/his own ideas and style to bear on the lesson.

Most of you know the classic algebra word problem type that has appeared frequently on standardized tests and math contests:

THE BIG QUESTION
Jack averaged 40 mi/hr going to school and 60 mi/hr returning from school over the same route. What was his average speed in mi/hr for the round trip?

Since there has been a decrease over the past 25 years in the number of word problems to which our students are exposed, some youngsters may not get to see one of these until reviewing for SATs or in their physics class.

From watching how students approach this type of question, I'm getting a sense that we need to introduce the basic concepts earlier on in middle school, which I am sure already occurs in some programs. In planning to teach methods of solving these kinds of problems, I usually tried to return to basic principles of math pedagogy - keep it simple and start with concrete numerical exercises that built on prior knowledge. What does all this jargon mean?

Start with a review of averages, then move on to combined averages before attempting to explain the round-trip rate problem!

[Concerned that such development will take too much time? There won't be enough time to review homework and provide enough practice for the homework assignment? My supervisors never threatened to fire me if a lesson lasted for more than one day and if, heaven forbid, I did not assign homework that first evening! Some ideas just cannot be rushed.]

Suggested Question #1:
Jack had a 70 avg on some tests and a 90 average on some other tests. Can his overall average be determined?

More specifically: When do you think 80 will be the correct answer? When will it not?

Comment:
Question 1 is intended to provoke thought and encourage an intuitive response, not a calculated answer!

Suggested Question #2:

Jack had a 70 average on his first 4 tests and a 90 average on his next 6 tests. What was his overall average for the 10 tests?

Note that I am suggesting beginning with problems to which middle school students may better be able to relate than a rate-time-distance question. The first question above is fundamental in developing the concept of the original rate problem.

These questions should help many students focus on the essential idea that we need to know how many are in each sub-group!

Since most students connect average to dividing a TOTAL by some quantity, they should feel comfortable in solving the average grade question as follows:

(TOTAL PTS)/(TOTAL NUMBER OF TESTS) to arrive at an average of 82.

BUT DON'T STOP THERE! Stress the UNITS of this result to build the rate concept:

AVG PTS/TEST = (TOTAL PTS)/(TOTAL TESTS)

Since students generally do not attach units to the 82, stress that the combined average is 82 PTS PER TEST or 82 PTS/TEST! BTW, not a bad time to mention that PER MEANS DIVIDE!!

Suggested Question #3:
Jack averaged 40 mi/hr for 2 hours, then 60 mi/hr for the next 2 hours. What was his average speed (rate), in mi/hr, for the 4 hours?

[Note the incremental development (commonly termed scaffolding in today's world!). Rather than jump to the abstraction of the original problem, we move on to the next logical step - giving them both the rates and the times for each part of the trip. In this case, we use equal times to provoke their thinking about why the result is also the simple arithmetic mean of the two rates. Each of us needs to make decisions about how many of these examples are needed before moving on to the main question.

Depending on the background and ability level of the group, you may be able to skip one or more of these suggested questions.
Further, you may already be thinking of placing these questions on a worksheet for students to try alone or in pairs, stopping and reviewing as needed.

Suggested Question #4:
Jack averaged 40 mi/hr for 4 hours, then 60 mi/hr for 2 hours. What was his average rate, in mi/hr, for the 6 hours?

Suggested Question #5:
Jack averaged 40 mi/hr for the first 120 miles of a trip, then 60 mi/hr for the remaining 120 miles. What was his average rate, in mi/hr, for the entire trip?
Key question: Why does it turn out that the answer is NOT 50 mi/hr?

Do you think your students would now be ready for the BIG QUESTION near the top of this post? OR do you think they would need at least one more interim problem? Again, could these questions have just as effectively been placed on a worksheet and given to students, working in pairs?

I'll leave the rest to our readers. Pls feel free to share your ideas, comments, thoughts and questions. There's no question in my mind that some of you would develop these ideas differently! Remember you can always email me personally at dmarain at geemail dot com (the last 4 words misspelled intentionally of course!). Unfortunately, I typically get little response from posts about instruction since most readers prefer to solve a challenging problem!

Final Comment: Note that I didn't once suggest that students use a short-cut for the original round-trip problem. Ok, so it is the
harmonic mean of the two rates, and can be calculated
from the formula: 2R1R2/(R1+R2).
But who would want to use that (uh, SATs, GREs, GMATs,...)???

## Monday, June 16, 2008

### A Geometry Classic - Chord and Tangent Riddle

Don't forget to submit your solution to this month's Mystery Mathematicianagram (ok, so I can't decide on a name yet!). We've received 3 correct solutions thus far and I will announce winners around the 20th.

As we wind down the school year, the problems below may come too late for students taking their final exams in geometry, but you may want to hold onto this classic puzzler for next year. I don't consider these overly challenging but I do feel they demonstrate some important mathematical ideas and problem-solving techniques. Further, encourage students to justify their reasoning since some may make assumptions from the diagram without verification. This will review some nice ideas from circles.

OVERVIEW OF PROBLEMS (see diagram)
For both questions, assume the circles are concentric, segment PQ is a chord in the larger circle and tangent to the smaller.

PART I
If PQ = 10, show the difference between the areas of the 2 circles is 25π.

PART II (the converse)
If the difference between the areas of the circles is 25π, show that the length of PQ must be 10.

Notes
(1) It is important for students to recognize that there are many possible pairs of concentric circles (varying radii) satisfying the hypotheses of these problems, yet the conclusions are unique! Some students will assume a 5-12-13 triangle is formed (not a bad problem-solving strategy), but stress that this is not the only possibility!
Remember, we're not restricting the radii to integer values.

(2) There is a classic math contest strategy for these questions that mathematicians love to employ - the "limiting case." Can you guess what I mean by this phrase?

## Friday, June 13, 2008

### A Math Riddle that gets better with 'Age'!

[Don't forget the Mystery Math Anagram for this month. Only two correct replies have been received thus far. I will announce the winners in a few days.]

Have you been wondering where the math challenges have gone on this blog? Here's one that I came across while reading David Baldacci's recent best seller, Simple Genius, just your usual tale of the dark world of mathematicians, codes and spies. Gee, math has become such an integral part of novels, TV shows and movies over the past few years, our students are going to think the life of a mathematician is really cool and exciting (which, as we all know, it is!).

Anyway, here is a paraphrasing of the problem (as long as I'm not copying the problem verbatim, the publisher granted me permission to discuss this):

Alex is as many months old as his grandpa is in years and about as many days old as his dad is in weeks. If the sum of their 3 ages is 140, how old is each?

Hint: This is a wonderful problem demonstrating the power of ratios. If you can solve it less than 20 seconds, then you're either an honorary member of Mensa or you could be the subject of Baldacci's next book!

(1) Like all riddles, the wording is somewhat convoluted and the mathematical assumptions are not explicitly stated. But that's part of the intrigue here. I will say that one needs to assume the ages are integers, but that's about it.

(2) In the novel, the problem is posed to a young mathematical prodigy named Viggie. While another mathematician in the room takes some time to solve it algebraically, Viggie comes up with the solution mentally in a few seconds. Can you!

(3) You may want to give this to middle school students, although the wording might frustrate them. You could demonstrate the idea with a concrete example or make it into a simpler problem:
Let's say that Alex is 96 months old, then his grandpa would be 96 years old. Now ask them to determine how old Alex's dad would be. This may be challenging enough...

(4) I'm naturally wondering what the source of this problem is. If anyone out there recognizes it, let us know its source!

## Monday, June 9, 2008

### MATH WARS - Advice for Parents

A few weeks ago I received a request for an interview from Jan Wilson, education columnist for The Parent Paper, a local publication here in northern NJ:

Hello Mr. Marain --

I am the education columnist for the Parent Paper and I am writing an article about math instruction, specifically about moving beyond the rhetoric of the math wars to discover which ways of instruction work best for K-5 students. It's going to be a fairly general article, designed for the parent who hasn't thought a lot about math before but becomes concerned because her child hasn't master times tables in 3rd grade, or isn't doing long division in 4th, for example.

The following is the reply I sent Jan from which she excerpted a few of my comments:

I am speaking both as a parent and a mathematics specialist with over 35 years in mathematics education at all levels. I have also been publishing a blog for math educators for the past year and a half. It was recognized by the Washington Post as one of the Top 10 Educational Blogs for 2007. Despite all the rhetoric, there are no bad programs out there in my opinion. The reform programs like Everyday Math and TERC do a fine job of developing children's number and spatial sense and address problem-solving as well. However, the district has to be committed to the expectation that children will practice their basic facts on a daily basis. Some children will master their times tables by the end of 3rd or 4th, some later on. However, they should all be expected to learn it by the end of 4th, even if some youngsters will take longer. Parents should not hesitate to ask the teacher and/or the principal if these expectations are in place. Further, they should ask if children are given some form of practice both in class and at home on a regular basis. Some children will learn from flash cards, others need to write each fact 5-10 times, others can benefit from games or software. Excellent online games like Timez Attack from Big Brainz can be played both in school and at home. The free version is quite good, but it will not work for every child. The only constant is that the expectation of learning these basics is stated in the currlculum and that this philosophy is actually implemented. If children's learning of basic facts is assessed regularly in class, then one can reasonably assume there is follow-through. Sometimes the only way to be sure of this is to talk to parents of children who have been through the program. Just remember: Playing games and problem-solving do not replace the need for children to memorize their facts. There is no way to get around this. If the district math program does not incorporate sufficient practice, then parents will need to supplement fact practice at home, even if it's only 10-15 minutes a day. Each child learns his/her own way, but each child must do something every day, using a reward system if needed to motivate them. In addition to skills practice supplementing existing programs as needed, parents should ask what kinds of problem-solving materials are used. Is the source of these problems restricted to what is provided by the publisher or are other resources utilized? For example, are teachers provided with the problem books from Singapore Math, which generally contains more difficult challenges than are normally found in our texts. Another question parents can ask if there is a new program is, "How have or will teachers be trained?" Is there a full-time Staff Developer working with teachers? Is there a math specialist for K-5 or 5-8? Short-term staff development is not nearly as effective as ongoing training, both for experienced and new teachers. It is important for parents to be aware that NJ Ask and other state testing will be undergoing significant changes in response to the recommendations of the National Math Panel, NCTM and organizations such as Achieve. All of these groups are calling for a reduction each year in the number of topics covered so that there will be more time for children to work toward mastery of important skills AND to develop greater depth of understanding. Teachers will be able to devote more time to provide both enrichment and reinforcement. This is an exciting opportunity. The Math Wars have been fueled by extremists on both sides. In the end, our children need a more balanced math education which will incorporate the best of the traditional and reformed.

Remember, I was writing this primarily for parents. These comments represent the same positions I have taken for the past 20 years and for which I have been challenged (a euphemism for attacked) by both "sides" for the same 20 years! Hey, I may be wrong but at least I am consistent!

## Tuesday, June 3, 2008

### Mystery Mathematician June '08 - An Anagram!

And now for something completely different...

A Math Mystery Anagram!
No picture this month!
If you like this variation, let me know...

"MEN-Y" THEOREM

No, it's not Monty Python, although the anagram contains 'Monty'! There are many anagram generators/solvers online so you could try those, although I did not find them useful here - I had to do this scramble myself. Please allow poetic license on the spelling of 'many' - perhaps there is a hidden clue there!

This mathematician was unique in so many ways - it is about time we paid proper tribute...

Our wordplay enthusiasts out there (and most math people are!) will probably solve this quickly but DON'T FORGET THE RULES: