Elementary POW, January 20-24, 1997


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The diagram shows the numbers 1 through 10 (in order) at the tips of 5 diameters. Only once does the sum of two adjacent numbers equal the sum of the opposite two numbers:

Elsewhere, for example,

Rearrange the numbers so that all sums are equal. You can expect more than one solution to this problem. How many basic solutions are there? (Do not include simple rotations of the same numbers - for example 1,2,3,4,5,6,7,8,9,10 would be the same as 2,3,4,5,6,7,8,9,10,1.)


This week's mentor is Jackie Roth, Grade 9, Germantown Academy, Fort Washington PA.

Correct Solutions submitted by:


Highlighted Solutions

Hello,

From the top mark on the circle (normally 0 degrees), these numbers are:

However, the area on the circle where you begin shouldn't matter (i.e. you could use the 72 degree mark for the 4, the 108 degree mark for the five, and so on).

>You can expect more than one solution to this problem. How many basic >solutions are there?

I've tried a couple of ways and have no idea how many there are. That's a tough problem.

I am a sixth grader at The Prairie School in Racine, WI.
Victor Osimitz


Mark Trama's 3rd Grade Class
Ithan Elementary School, Bryn Mawr, PA
E-Mail: mtrama@itrc.dciu.k12.pa.us

We all worked on our own at home and between us generated 8 different solutions:

  1. Mike, Marina, Jim, George, Peter, Scott C., Claire : 6, 2, 8, 4, 10, 1, 7, 3, 9, 5
  2. Scott P., Robby: 9, 2, 10, 1, 8, 4, 7, 5, 6, 3
  3. Yiqiong: 10, 2, 8, 1, 9, 5, 7, 3, 6, 4
  4. Eric: 10, 1, 8, 3, 6, 9, 2, 7, 4, 5
  5. Gi-Soo: 10, 1, 9, 2, 8, 5, 6, 4, 7, 3
  6. Katie:10, 1, 8, 2, 9, 5, 6, 3, 7, 4
  7. Samantha: 10, 7, 6, 1, 4, 9, 8, 5, 2, 3

And lastly, Claire arranged the numbers a second way also - 10, 1, 9, 3, 7, 5, 6, 4, 8, 2 - She had the 10 and 1 at the top of the circle and the 5 and 6 at the bottom. She had one of those "a-ha" moments when she discovered that if you write the differences between neighboring numbers in the space between the numbers, that these differences show a symmetry. For example, 6 and 5 are neighboring numbers and their difference is 1. When you head out 1 spot in each direction, the 6 and 4 are neighbors and the 5 and 7 are neighbors - they each have a difference of 2. The 8 and 4 and the 7 and 3 each have a difference of 4. The differences go up each side from the bottom 1, 2, 4, 6, 8, and then lastly, 9 at the top between the 10 and the 1.

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