# IntMath Newsletter: Interactive ellipses, Wolfram Education Portal

By Murray Bourne, 17 Feb 2012

17 February 2012

In this Newsletter:

1. Interactive ellipse graphs

2. Wolfram's Education Portal

3. Puzzle

4. IntMath Poll: Feelings about math

5. Friday math movies

6. Final thought - moving slowly

## 1. Interactive ellipse graphs

New on IntMath.com! Here are some graphs that help you understand basic concepts of ellipses. It doesn't matter if you haven't studied this topic yet - it will still be useful. Go to: |

## 2. Wolfram's Education Portal

This is a new offering (free for now) from Worlfram, the makers of Mathematica, Wolfram|Alpha and the Demonstrations Project.

They have developed a series of math courses using their new CDF (Computable Document Format) technology, which are basically interactive text books.

Here's the link: Wolfram Education Portal

The courses available at the bottom of that page so far include several **algebra** topics like:

- Equations and Functions
- Graphs of Equations and Functions
- Graphing Linear Inequalities
- Introduction to Probability
- Solving Systems of Equations and Inequalities
- Exponential Functions
- Quadratic Equations and Functions

Coming soon is **calculus**, and a** math question practice **feature.

You'll need to download the (free) CDF player (it's easy and quick) and sign up (also painless). In tiny font, it says:

"Wolfram Education Portal is now is avaliable for free, but it might be paid after the official release."

Certainly worth checking out while it's free! Wolfram Education Portal

## 3. Puzzle

I had many requests to bring back the puzzle feature. So here we go.

**Question: **The Egyptians used only unit fractions (that is, the numerator was 1). So they would write 3/5 as 1/2 + 1/10. How would they write 11/13?

You can only use addition (not minus) and use as few fractions as possible. You can submit your answer here.

## 4. IntMath poll: Feelings about Math

The recent IntMath Poll asked readers how they feel about math. Here are the results.

The best way to describe how I feel about math is:

I enjoy math

41%

It’s OK but I find it hard

30%

I hate math

24%

No strong opinion

4%

It's sad that 1/4 of the respondents answered with a negative view about math. Hopefully IntMath has helped some of them to like it some more!

**Current poll: **The current poll asks if you think the math you are studying will be useful for your future job.

You can answer on any page in IntMath.com

## 5. Friday math movies

How can we fix education? This is a clever animation of Ken Robinson's ideas, talking about why education often doesn't work as intended. |

Here's a story about a brain scientist who had a massive stroke at age 37 - and who lived to tell the fascinating tale. |

## 6. Final thought: moving slowly

For many students, math class goes very slowly. Here's a Chinese saying that's worth thinking about.

Don't worry about moving slowly, worry about standing still. [Chinese proverb]

Until next time, enjoy whatever you learn.

See the 25 Comments below.

17 Feb 2012 at 5:17 pm [Comment permalink]

1/13 + 1/13 + ......thirteen times.

17 Feb 2012 at 5:46 pm [Comment permalink]

used one loop

100: n=n+1

test =1/n

sum =sum +test

if sum < 11/13 then 100

sum=sum-test

goto 100

11/13 = (1/2) + (1/3) + (1/78)

good problem

17 Feb 2012 at 10:43 pm [Comment permalink]

11/13 = 33/39 = 13/39 + 13/39 + 7/39

= 1/3 + 1/3 + 3/39 + 3/39 + 1/39

= 1/3 + 1/3 + 1/13 + 1/13 + 1/39

18 Feb 2012 at 1:15 am [Comment permalink]

1/13+10/13=11/13

18 Feb 2012 at 1:34 am [Comment permalink]

1/13+1/65+1/65

18 Feb 2012 at 3:21 am [Comment permalink]

1/2+1/4+1/13+1/52

18 Feb 2012 at 4:33 am [Comment permalink]

The answer is

11/13 = 1/2 + 1/3 + 1/78

18 Feb 2012 at 5:29 am [Comment permalink]

(1/4) + (1/(52)) + (1/(13)) + (1/2)

18 Feb 2012 at 5:52 am [Comment permalink]

1/3 + 1/2 + 1/78 = 11/13

18 Feb 2012 at 6:15 am [Comment permalink]

1/2 + 1/3 + 1/78 .

18 Feb 2012 at 6:28 am [Comment permalink]

1/2+1/3+1/78 = 11/13

18 Feb 2012 at 7:58 am [Comment permalink]

My answer to puzzle 11/13= 1/78 + 1/12 + 1/4 + 1/2

19 Feb 2012 at 12:36 am [Comment permalink]

thank you sir to this informative article.I absolutely benefited from this article.

19 Feb 2012 at 9:21 am [Comment permalink]

It seemed to me that starting with an even denominator would help so I expressed the fraction in different forms. For each, I removed the 1/2 and looked at the remainder. If it was broken so that one piece was a unit fraction, what would be left over? Repeating the exercise a few times led to 11/13 = 1/2 + 1/3 + 1/78

11/13 =

22/26 = 13/26 + 9/26 = 1/2 + 1/26 + 8/26 = 1/2 + 1/26 + 4/13

33/39 =

44/52 = 26/52 + 18/52 = 1/2 + 9/26 =

55/65

66/78 = 39/78 + 27/78 = 1/2 + 26/78 + 1/78 = 1/2 + 1/3 + 1/78

39/78 + 26/78 + 1/78 = 66/78 = 11/13

19 Feb 2012 at 8:04 pm [Comment permalink]

Thanks everyone for your replies on the Eqyptian fraction problem.

You can see why mathematicians worked hard to come up with a better numeration system. I'm glad we have the base 10 system!

20 Feb 2012 at 7:49 am [Comment permalink]

11/13 = 6/13 + 5/13

Thanks very much for this unit fraction and hope to get more from you.

20 Feb 2012 at 8:24 am [Comment permalink]

1/2 + 1/4 + 1/8 + 1/26

20 Feb 2012 at 8:25 am [Comment permalink]

Fun problem. Sent it to my grandson who has taken fractions.

20 Feb 2012 at 12:18 pm [Comment permalink]

It is easy; 11/13 = 1/2 + 1/3 + 1/78

First take the hihest unit fraction an subtract it from 11/13.

Then take the next highest unit fraction, which is 1/3 and subtract it from 11/13 - 1/2.

22/26 - 13/26 = 9/26 note 9/26 > 1/3

27/78 - 1/3 = 27/78 - 26/78 = 1/78

20 Feb 2012 at 11:27 pm [Comment permalink]

Geez I can't do arithmethic any more. the answer I get is

1/2 + 1/3 + 1/78

21 Feb 2012 at 2:46 pm [Comment permalink]

1/2 + 1/4 +1/13 + 1/52 = 44/52 = 11/13

22 Feb 2012 at 4:29 am [Comment permalink]

1/2+1/4+1/13+1/52 = 44/52 = 11/13

23 Feb 2012 at 5:53 am [Comment permalink]

1/2+1/4+1/8+1/28=11/13

4 Mar 2012 at 9:17 pm [Comment permalink]

11/13=1/2+9/29..ans

sol: 1/2+9/26=(13+9)/26

=22/26

=11/13. ans

5 Mar 2012 at 9:19 pm [Comment permalink]

1/2 + 1/3 + 1/78.. dats it..