# IntMath Newsletter: Interactive ellipses, Wolfram Education Portal

By Murray Bourne, 17 Feb 2012

17 February 2012

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: Interactive ellipse graphs

## 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

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

"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 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

 (a) Ken Robinson animated 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. Friday math movie: Ken Robinson animated
 (b) How it feels to have a stroke Here's a story about a brain scientist who had a massive stroke at age 37 - and who lived to tell the fascinating tale. Friday math movie: How it feels to have a stroke

## 6. Final thought: moving slowly

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

Until next time, enjoy whatever you learn.

1. Dineth says:

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

2. don miller says:

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

3. guido verbraeken says:

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

1/13+10/13=11/13

5. CHARLES TEMBO says:

1/13+1/65+1/65

6. Wendy says:

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

7. Tomas Garza says:

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

8. Sachin Sapkal says:

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

9. Laureli Sluggett says:

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

10. Greg says:

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

11. ARUN KUMAR A says:

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

12. Karen Remington says:

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

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

14. Francis Kisner says:

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

15. Murray says:

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!

16. Brew Mowl says:

11/13 = 6/13 + 5/13

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

17. George Walters says:

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

18. George Walters says:

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

19. SIVY FARHI says:

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. George Walters says:

Geez I can't do arithmethic any more. the answer I get is
1/2 + 1/3 + 1/78

21. John says:

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

22. Rina Sengupta says:

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

23. Wynill says:

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

24. nkupiarity says:

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

sol: 1/2+9/26=(13+9)/26
=22/26
=11/13. ans

25. Saran says:

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

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