March 2015
Problem of the Month

Easy As 1, 2, 3 ...

There are just two ways to insert four plus or minus signs between the digits 123456789 to yield a sum of 1:
      1 + 23 - 45 - 67 + 89 = 1
      1 - 23 + 45 + 67 - 89 = 1

Now, see if you can insert four plus or minus signs in the sequence 987654321 to make a sum of 1.   There is only one solution.

Solution to the Problem:

98 - 76 - 54 + 32 + 1 = 1

James Alarie wrote:
You didn't include a zero in either the ascending nor decending string.

Putting a zero at the beginning of either string gives the same results as without it.   Putting the zero at the end of either string results in no solutions.

Correctly solved by:

1. James Alarie	Flint, Michigan
2. Riley Dolezal	Mountain View High School, Mountain View, Wyoming
3. Dalton Hereford	Mountain View High School, Mountain View, Wyoming
4. Chris Stringer	Mountain View High School, Mountain View, Wyoming
5. Auriella Haslett	Mountain View High School, Mountain View, Wyoming
6. Hannah Behunin	Mountain View High School, Mountain View, Wyoming
7. Kayle Rippetoe	Mountain View High School, Mountain View, Wyoming
8. Brooks Garris	Lake View High School, Lake View, South Carolina
9. Shay Martin	Mountain View High School, Mountain View, Wyoming
10. Kam Dellinger	Mountain View High School, Mountain View, Wyoming
11. Chad Fore	Gate City, Virginia
12. Braydon Saxton	Mountain View High School, Mountain View, Wyoming
13. Nathan Atchley	Las Vegas, Nevada
14. Shay Martin	Mountain View High School, Mountain View, Wyoming
15. Isaac Kampman	Mountain View High School, Mountain View, Wyoming
16. Colton Roach	Mountain View High School, Mountain View, Wyoming
17. Marley Newton	Mountain View High School, Mountain View, Wyoming
18. Ryan Woody	Mountain View High School, Mountain View, Wyoming
19. Austin Houskeeper	Mountain View High School, Mountain View, Wyoming
20. Caleb Flake	Mountain View High School, Mountain View, Wyoming
21. Cheyenne Dunn	Mountain View High School, Mountain View, Wyoming
22. Austin Smith	Mountain View High School, Mountain View, Wyoming
23. Taylor Meeks	Mountain View High School, Mountain View, Wyoming
24. Bailey Lupher	Mountain View High School, Mountain View, Wyoming
25. Keith Mealy	Cincinnati, Ohio
26. Alexis Stoddard	Mountain View High School, Mountain View, Wyoming
27. Hannah Stoddard	Mountain View High School, Mountain View, Wyoming
28. Michael Reilly	Silver Spring, Maryland

Send any comments or questions to: David Pleacher